cylindrical pool filter cartridge with blue edges and a label featuring a cartoon filter character giving thumbs up
tall cylindrical pool filter cartridge with pleated white material and blue plastic caps on both ends against a white background
Cylindrical pool filter cartridge with blue plastic end caps and white pleated filter material inside
Cylindrical pool filter cartridge with blue plastic end cap and pleated filter material inside a hollow core

Unicel C-4325 Replacement Filter Cartridge for Hayward MicroStar-Clear C225 & Pentair Commander II | 25 Sq. Ft. | 11 7/8"

Regular price$23.99
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SKU:
C-4325
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About This Item

The Unicel C-4325 is a 4000 Series 25 sq. ft. replacement filter cartridge engineered for the Hayward MicroStar-Clear C225 and Pentair-American Products Commander II in-line pool filter systems. Featuring 138 pleats of 3 oz. Reemay® 2033 spunbond polyester media, this cartridge delivers the filtration surface area and dimensional precision needed to keep your water clear and your system running at rated capacity.

⚠️ IMPORTANT: FITMENT NOTE — OEM DIMENSION VARIANCE
The original Hayward MicroStar-Clear C225 cartridge measures 4-3/4" OD and 11-13/16" overall length. The original American Products Commander II cartridge measures 4-11/16" OD. The Unicel C-4325 is engineered at 4 5/8" OD — a precision replacement dimension designed to seat and seal correctly within both filter housings. If you are measuring your old cartridge, these small OD differences are expected and normal for a Unicel replacement.

Specifications

Filter Area 25 sq. ft.
Length 11 7/8"
Outer Diameter 4 5/8"
Top Inner Diameter 2 1/16"
Bottom Inner Diameter 2 1/16"
Material 3 oz. Reemay® 2033
Pleat Count 138
Top Cap: Open
Top Cap
Bottom Cap: Open
Bottom Cap

Fits Into:

OEM Brand Filter Model OEM Part Number Notes
Apollo Spas Select models — verify dimensions before ordering
Emerald Spas Select models — verify dimensions before ordering
Hayward MicroStar-Clear C225 (in-line) CX225RE OEM original is 4-3/4" OD and 11-13/16" overall length
Pentair (American Products) Commander II (in-line) 57010500 OEM original is 4-11/16" OD; legacy American Products system
Sonoma Spas Select models — verify dimensions before ordering

(This is not an exhaustive list.)

Pro Tip: Before ordering, measure your existing cartridge's outer diameter at the widest point and overall length end-to-end. For Hayward MicroStar-Clear C225 owners: your OEM cartridge measures 4-3/4" OD and 11-13/16" length — the C-4325 at 4 5/8" OD is the correct Unicel replacement for that system. For Apollo, Emerald, and Sonoma Spa owners without a specific OEM part number, confirm both the OD and length match 4 5/8" × 11 7/8" before placing your order.

Also known as: C4325

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Unicel Filter Cartridges and DE Grids

About Unicel Filter Cartridges and DE Grids

The "Gold Standard" of Replacement Cartridges
For over 50 years, Unicel (Meissner Mfg.) has been the professional's choice for restoring pool water clarity. While generic "knock-off" filters often use cheap, fuzzy fabric that clogs quickly, Unicel uses genuine Reemay® Filtration Media. This patented synthetic fiber features a unique trilobal shape that traps significantly more dirt and oils without choking your pump's water flow. Based in California, Unicel doesn't just copy filter dimensions; they engineer them to strict Original Equipment Manufacturer (OEM) specifications. This ensures a "lock-tight" fit in your filter tank, preventing debris from bypassing the system and returning to your pool.

Why We Trust Unicel Filter Cartridges and DE Grids
Genuine Reemay® Media: Uses continuous trilobal fibers to capture microscopic debris without restricting water flow.

Precision "Exact Fit": Engineered to match your tank's original specifications for a 100% leak-free seal.

Made in the USA: Manufactured in California with heavy-duty urethane end caps that resist cracking under pressure.

Longer Lifespan: Sharp, rigid pleats resist collapsing during cleaning, meaning you buy fewer replacements over time.

More about Pool and Spa Filter Cartridges

Complete Your Pool Care Routine

Essential Pairing
Filter Cleaning Chemicals for All Types of Pool & Spa Filters

Using a specialized cleaner like FilterWash helps release deeply embedded oils and minerals that standard rinsing leaves behind.

Shop Filter Cleaning Chemicals for All Types of Pool & Spa Filters
Highly Recommended
Pool and Spa Plumbing Lubricants

Every time you open your filter tank, you must lubricate the O-ring to prevent dangerous leaks and ensure a watertight seal.

Shop Pool and Spa Plumbing Lubricants
Pro Tip: Don't Forget
Pool Test Kits and Water Analysis Tools

Balanced water pH prevents calcium scale from hardening your filter fabric and ruining your new cartridges.

Shop Pool Test Kits and Water Analysis Tools

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