Cart, 25sqft,2-1/8″ot,2-1/8″ob,4-15/16″dia,13-5/16″L,4oz | 42521

💧 Darlly Filtration 42521 Replacement Filter Cartridge — 25 sq ft

This is a 25 sq ft replacement filter cartridge from Darlly Filtration, part number 42521. It measures 4-15/16″ in diameter and 13-5/16″ long, with a 2-1/8″ open top and a 2-1/8″ open bottom. It uses 4 oz filter media. It is listed for the equipment shown below, so check the model on your own unit against that list. If your old part carries one of the cross-reference numbers further down, this is listed as its alternative.

📏 Specifications

✅ Listed for

• In-Line
• Skim Filter 25sqft (4oz)
• Rainbow Dynamic 25sqft (4oz)
• Verti-Pak 25sqft In-Line
• Waterway Top Load Filter
• Waterway Ultra Skim Filter

🛁 Spa makes it is listed for

Alps Spas, Aries Spas, Baker Hydro, Blue Pacific, Continental Leisure, Ester W/Johnny W, Haughs/Niagara Whirlpool, Heldor Spas, Hydro Pool, Hydro Pool/Serenity Spas, Icon Health & Spas, J.E.M. Spas, Johnny W/Ester W, Niagara Whirlpool (Haughs), PDC Spas, Premier Springwater, Rainbow/Pentair, Sequoia Design, Serenity Spas (Hydro Pool), Warm Springs Spas, Waterway.

🔄 Cross-reference part numbers

These part numbers are listed as alternatives for this part.

📐 How to check the size

Measure your old cartridge from end to end for the length, and across the pleats at the widest point for the diameter. Then check the hole in the center of each end cap: an open end has a hole straight through, a closed end is solid. All of these should match the specifications table above.