Water Filter Cartridge Size Chart: Complete Compatibility Guide (2026)

Choosing the wrong cartridge size is one of the most common and costly mistakes water filter importers make. A 10” slim line cartridge will not fit a Big Blue housing. A U-8 quick-connect will not snap into a U-11 bracket. And a K2 replacement that doesn’t match the Aquaphor locking collar arrives, gets tested, and gets returned.

This guide covers every major cartridge form factor used in residential and light commercial water filtration — dimensions, housing compatibility, flow rates, media options, and MOQ benchmarks from a Chinese OEM factory perspective. Bookmark it before your next sourcing call.

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1. Standard Cartridge Sizes

Standard cartridges are the backbone of point-of-use water filtration globally. They fit into screw-cap sump housings (also called “canister” or “vessel” housings) and are available in polypropylene, GAC, carbon block, UF, and RO versions.

The two diameter families are Slim Line (2.5” OD) and Big Blue (4.5” OD). Within each family, lengths of 10” and 20” are the dominant SKUs.

Size Name	Dimensions (D × L)	Common Names	Compatible Housings	Typical Flow Rate
10” Slim Line	2.5” × 9.75”	Standard 10”, SL-10	10” standard housing (any brand)	1–2 GPM
20” Slim Line	2.5” × 19.75”	Standard 20”, SL-20	20” standard housing	1–2 GPM
10” Big Blue	4.5” × 9.75”	BB-10, Jumbo 10”	Big Blue 10” housing	4–8 GPM
20” Big Blue	4.5” × 19.75”	BB-20, Jumbo 20”	Big Blue 20” housing	4–8 GPM
10” Inline	2” × 9.75”	Inline 10”, T33 style	Dedicated inline housing	0.5–1 GPM

Key compatibility rules:

• Slim Line cartridges are interchangeable across housing brands as long as the end-cap type matches (DOE vs. SOE). The 10” and 20” are not interchangeable — never put a 20” cartridge in a 10” housing.
• Big Blue housings require Big Blue cartridges. The 4.5” diameter is a hard stop; slim line cartridges will float inside and bypass.
• Big Blue is the standard for commercial and high-flow pre-treatment. For an importer serving restaurants, hotels, or light industrial buyers, the commercial Big Blue cartridge line is a separate category from residential slim line.

For full specifications and OEM options on standard cartridges, see our standard cartridge catalog.

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2. Quick-Connect Cartridge Compatibility

Quick-connect (snap-in) cartridges replaced screw-cap housings in most modern under-sink and countertop systems. Instead of unscrewing a sump housing, the user simply pushes a button and pulls the cartridge straight down or sideways.

There are two primary quick-connect connector geometries used in the Chinese and Russian markets:

• I-type (inline): Cartridge installs vertically with a single port at the bottom. Common in single-stage undersink setups.
• U-type: Cartridge installs with ports at both ends of the base, forming a “U” flow path. Dominant in multi-stage compact systems.

Model	Dimensions (D × L)	Media Options	Compatible Systems	MOQ
I-10	50mm × 254mm (10”)	PP, GAC, CTO, T33, UF	Standard I-type 10” brackets	500 pcs
I-11	50mm × 280mm (11”)	PP, GAC, CTO, T33, UF	Standard I-type 11” brackets	500 pcs
U-6	50mm × 152mm (6”)	GAC, CTO, T33	Compact 3-stage under-sink	500 pcs
U-8	50mm × 203mm (8”)	PP, GAC, CTO, T33, UF	Standard U-type 8” brackets	500 pcs
U-11	50mm × 280mm (11”)	PP, GAC, CTO, T33, UF	Standard U-type 11” brackets	500 pcs

Compatibility warnings:

• I-10 and I-11 use the same port diameter but different cartridge lengths. An I-10 cartridge placed in an I-11 bracket will not lock; there is typically a 26mm length difference that prevents engagement.
• U-6, U-8, and U-11 all use the same port footprint in some bracket families, but the cartridge body length determines which size the locking collar engages. Mixing sizes causes leaks or incomplete lock.
• Some Russian OEM brands (Aquaphor, Filtrus, Geyser) use proprietary port angles. Before quoting replacements, confirm port center-to-center distance and collar diameter.

Browse our full quick-connect cartridge range with drawings available on request.

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3. Aquaphor-Compatible Cartridges

Aquaphor is the dominant water filter brand in Russia and the CIS. Their pitcher and countertop systems use a snap-on cartridge format with a distinctive bayonet or quarter-turn locking mechanism. The replacement market is substantial — millions of Aquaphor units are in homes across Russia, Kazakhstan, Ukraine, and Belarus.

XZH produces a full range of Aquaphor-compatible snap-on cartridges under our own label or for private-label OEM customers. These are the most frequently requested Aquaphor-format models:

XZH Model	Replaces Aquaphor	Compatible Aquaphor Systems	Filter Media	MOQ
XZH-K2	Aquaphor B100-6	Crystal, Crystal H	Carbon block + ion exchange	1,000 pcs
XZH-K3	Aquaphor B100-7	Morion, Trio	Carbon block + silver	1,000 pcs
XZH-K5	Aquaphor B150	Favorit, Prestige	Enhanced carbon block	1,000 pcs
XZH-K7	Aquaphor B200	Maxfor, Crystal H	Carbon + mineral filter	1,000 pcs
XZH-K7M	Aquaphor B200H	Crystal H (hard water version)	Carbon + anti-scale	1,000 pcs
XZH-KH	Aquaphor B100-25	Trio, Morion, Favorit	Softening + carbon block	1,000 pcs

Notes for distributors:

• All XZH Aquaphor-compatible cartridges use NSF-grade activated carbon from domestic Chinese suppliers (coconut shell, iodine value ≥1,000 mg/g).
• The bayonet locking collar is dimensionally equivalent to the Aquaphor original. No modification to the housing is required.
• Private-label packaging (box design, language, brand name) is available from MOQ 2,000 pcs per model.
• Certification documentation (SGS test reports, ISO 9001) available for distributor use.

See the full Aquaphor-compatible cartridge catalog or request samples.

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4. Filter Media Comparison Chart

The cartridge form factor determines where it fits. The filter media determines what it removes. These are not interchangeable choices — a GAC cartridge in the second stage of an RO system does a completely different job than a GAC cartridge in a standalone undersink filter.

Media	Filtration Rating	Removes	Lifespan	Best For	Price Tier
PP Sediment	1–50 micron	Sand, rust, silt, particles	3–6 months	Pre-filter, well water, tanker supply	Low ($0.15–0.50/pc)
GAC (Granular Activated Carbon)	N/A (adsorption)	Chlorine, taste, odor, VOCs	6–12 months	Municipal water, pre-RO, drinking water	Low-Mid ($0.40–1.20/pc)
CTO Carbon Block	0.5–5 micron	Chlorine, cysts, sediment, taste	6–12 months	Drinking water, RO pre-treatment	Mid ($0.80–2.50/pc)
T33 Post-Carbon	N/A (polishing)	Residual taste, odor after RO	12 months	RO post-filter (taste polish)	Mid ($0.60–1.80/pc)
UF Membrane	0.01–0.1 micron	Bacteria, protozoa, colloids	12–24 months	Bacteria-risk markets, no RO needed	Mid-High ($1.50–4.00/pc)
RO Membrane	0.0001 micron	TDS, heavy metals, nitrates, fluoride	24–36 months	High-TDS water, arsenic, fluoride	High ($3.00–12.00/pc)

Selecting media by market:

• Russia/CIS: Carbon block (K-series) for pitcher systems. UF for countertop units. RO for under-sink. PP sediment for dacha (countryside home) pre-filters.
• Middle East: RO is mandatory due to high TDS groundwater. PP sediment pre-filter essential to protect RO membrane.
• Southeast Asia: UF strong market (concerns about bacteria, preference to avoid electricity for RO pump). CTO carbon block growing fast.
• Europe: Carbon block + UF combination dominant. Regulatory scrutiny on NSF/ANSI 42 and 58 certification.

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5. Shower Filter Cartridge Sizes

Shower filters use different cartridge geometries than drinking water systems. Most are designed to fit inside a cylindrical inline housing installed between the shower arm and the showerhead. The cartridge itself is a compact cylinder with male/female thread ends.

XZH produces five shower filter cartridge series. Dimensions and fitting specifications:

Series	Outer Diameter	Length	Thread/Fitting	Media	Housing Compatibility
B Series	55mm	100mm	1/2” Male NPT both ends	KDF-55 + calcium sulfite	B-type standard shower housing
C Series	60mm	120mm	1/2” Female NPT both ends	KDF-55 + activated carbon	C-type shower housing, twist-lock
D Series	65mm	150mm	3/4” Male NPT both ends	Vitamin C + calcium sulfite	D-type high-flow housing
E Series	55mm	120mm	Universal 1/2” NPT	Activated carbon + KDF	Multi-brand E-type housing
F Series	70mm	180mm	1/2” Male NPT + bayonet top	KDF-85 (heavy metals) + carbon	F-type handheld shower housing

Key data points for shower filter buyers:

• KDF-55 removes chlorine and controls bacteria via redox reaction. Effective in hot water (unlike activated carbon, which degrades above 38°C).
• Vitamin C (ascorbic acid) neutralizes both chlorine and chloramines. Increasingly requested by EU-market buyers due to chloramine use in water treatment.
• KDF-85 targets heavy metals (iron, lead, hydrogen sulfide). Specified by commercial buyers (gyms, hotels) in regions with older pipe infrastructure.
• Lifespan is typically quoted as 3–6 months or 10,000–15,000 liters, whichever comes first.
• OEM options: custom media blend, private-label housing color, retail packaging in any language.

Browse our shower filter product range.

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6. How to Choose the Right Cartridge Size

Use this decision flow before placing a sourcing inquiry:

Step 1: What is the housing type?

• Screw-cap sump housing → go to Step 2
• Snap-in / quick-connect housing → go to Step 3
• Shower inline housing → Step 5
• Pitcher / countertop snap-on → Step 4

Step 2: Standard housing — what is the housing diameter?

• 10” or 20” housing, diameter ~3.5” inside → Slim Line cartridge (2.5” OD)
• 10” or 20” housing, diameter ~5.5” inside → Big Blue cartridge (4.5” OD)
• Confirm with housing inner diameter measurement. When in doubt, ask the housing manufacturer for the cartridge OD specification.

Step 3: Quick-connect — what is the form factor?

• Single port at bottom → I-type. Measure cartridge length: 10” (254mm) or 11” (280mm)?
• Dual ports at base → U-type. Measure cartridge length: 6” (152mm), 8” (203mm), or 11” (280mm)?
• For replacements: remove the existing cartridge and measure OD and OAL (overall length) before ordering.

Step 4: Pitcher/countertop — what is the brand?

• Aquaphor housing → check our XZH Aquaphor-compatible range
• Other brand → send us a sample or drawing. We will assess compatibility and quote for OEM production.

Step 5: Shower filter — what is the housing series?

• Check the housing label for the series letter (B/C/D/E/F) or measure the cartridge OD and length.
• Thread type: most residential shower housings are 1/2” NPT. Commercial/European housings may be 3/4” BSP — confirm before ordering.

Step 6: What media do you need?

• Chlorine / taste / odor → GAC or CTO carbon block
• Bacteria / protozoa → UF membrane
• Heavy metals / high TDS → RO membrane
• Particles / rust / sediment → PP sediment (always as first stage)
• Multi-stage system → combine in sequence: PP → GAC/CTO → UF or RO → T33 post-carbon

If you’re building a private-label product line and need help specifying a complete system, our OEM manufacturing service includes media selection, housing sourcing, and custom packaging.

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7. Frequently Asked Questions

What size water filter cartridge do I need?

The answer depends on your housing type, not personal preference. Measure the inner diameter of your filter housing sump: approximately 3.5” inner diameter takes a 2.5” OD slim line cartridge. Approximately 5.5” inner diameter takes a 4.5” OD Big Blue cartridge. For quick-connect systems, identify I-type or U-type and measure the length of the existing cartridge.

Are 10 inch water filters universal?

No. “10 inch” refers only to the cartridge length, not the diameter. A 10” slim line (2.5” OD) and a 10” Big Blue (4.5” OD) are both 10 inches long but are completely incompatible with each other’s housings. Within the same diameter family, most 10” cartridges from different brands are interchangeable for DOE (double open-end) models, but SOE (single open-end) end caps may differ.

Can I use a 20 inch filter in a 10 inch housing?

No. A 20” cartridge is physically too long to fit in a 10” housing sump. The reverse is also true — a 10” cartridge placed in a 20” housing will allow water to bypass around the short cartridge, providing essentially no filtration. Always match cartridge length to housing length.

What is the difference between slim line and Big Blue?

Slim line cartridges are 2.5” in diameter and handle 1–2 GPM, making them suitable for residential point-of-use systems. Big Blue cartridges are 4.5” in diameter and handle 4–8 GPM, making them suitable for whole-house systems, commercial kitchens, restaurants, and industrial pre-treatment. The larger cross-section of Big Blue reduces pressure drop and increases filter surface area for longer service life. See our commercial Big Blue range.

What is the difference between GAC and CTO carbon block?

GAC (granular activated carbon) uses loose carbon granules. Water channels through the granules, giving variable contact time. Lower backpressure, lower cost, suitable for taste/odor applications. CTO carbon block compresses carbon powder into a solid block. Water is forced through the block, ensuring full contact and enabling the cartridge to act as both a chemical adsorber (chlorine/VOC removal) and a mechanical filter (down to 0.5 micron). CTO costs more but provides better and more consistent performance. For drinking water and RO pre-treatment, CTO is generally specified.

Are Aquaphor cartridges compatible with other brands?

Aquaphor uses a proprietary bayonet locking collar. Their cartridges are not directly compatible with Brita, Ecosoft, or other pitcher brands. However, third-party manufacturers including XZH produce cartridges dimensionally equivalent to Aquaphor originals. These aftermarket cartridges fit Aquaphor housings without modification. Importers building a distributor business in the Russian market should note that Aquaphor’s installed base makes the replacement cartridge segment extremely valuable.

What is the MOQ for custom-size cartridges?

For standard sizes (10” slim line, 20” slim line, 10”/20” Big Blue), MOQ starts at 500 pcs per media type. For custom dimensions (non-standard OD, OAL, or end-cap configuration), MOQ is typically 2,000 pcs due to tooling requirements. Quick-connect cartridges (I-type, U-type) start at 500 pcs. Aquaphor-compatible snap-on cartridges start at 1,000 pcs. Custom OEM packaging can be added from MOQ 2,000 pcs. Contact our sales team for a formal quote.

How do I verify cartridge compatibility before placing a bulk order?

Request samples before committing. Any reputable Chinese OEM factory will supply 5–20 sample units for a courier charge. XZH provides samples with full test reports (pressure test, flow rate, filtration efficiency). If you are replacing an existing brand in your product line, send us a sample of the current cartridge — we will confirm dimensional compatibility and produce a matching unit for your evaluation.

What certifications are available for OEM water filter cartridges?

The most common certifications requested by market are: NSF/ANSI 42 and 58 (USA, Canada, increasingly Europe), CE marking (EU), SGS or Intertek test reports (general export), and GOST-R or EAC certification (Russia/CIS). XZH holds ISO 9001 and can provide SGS test reports. NSF certification requires application by the brand owner, not the factory — we support the process with material disclosure documents. For details, see our product catalog and contact us for market-specific certification guidance.

Can I mix cartridges from different brands in the same multi-stage system?

For standard sump housings: yes, as long as OD and length match. The housing is brand-agnostic. For quick-connect systems: mixing brands is riskier because port geometry and locking collar tolerances vary. If your quick-connect bracket is from a specific brand, request cartridges qualified against that bracket. For Aquaphor systems: only Aquaphor-dimensionally-equivalent cartridges (OEM or third-party compatible) should be used.

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Summary: Cartridge Size Reference

System Type	Key Dimension	What to Measure	Where to Look
Standard sump housing	Cartridge OD and length	Housing inner diameter, sump depth	Standard cartridges
Quick-connect I-type	Cartridge OAL	Port diameter, cartridge length	Quick-connect
Quick-connect U-type	Cartridge OAL	Port center-to-center, cartridge length	Quick-connect
Aquaphor pitcher/countertop	Bayonet collar diameter	Housing model number	Aquaphor-compatible
Shower filter inline	Cartridge OD and thread	Thread type, housing series letter	Shower filters
Big Blue commercial	Cartridge OD (4.5”) and length	Housing sump inner diameter	Commercial/Big Blue

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Get the Right Cartridge — First Time

Sizing errors on bulk orders are expensive. Before you commit to a container, verify: housing type, cartridge OD, cartridge length, end-cap configuration, and media specification. If any of these are unclear, send us a photo of the existing cartridge or housing label.

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