This 3 pack O-Rings by iFilters are used to seal water filter housings. It has an ID of 3.5" and made of nitrile butadiene rubber (Buna-N) for flexibility and resistance to abrasion and tearing. Fits many standard size housings for that use 10" filters, which are used in various applications, such as drinking water purification, whole house, industrial processes, and more. The ORING-25 is the Original OEM replacement for the following iFilters filtration systems: LWH-D, LWHSD, LWHGAC, CNTP-1W, CNTP-1C, U200UV, U200, U300UV, U300, RO-550, RO-575, RO-5100, and RO-S50. Compatible with filtration systems made by: iFilters, APEC, iSpring, Geekpure, Olympia Water Systems, and many more Fully compatible: APEC ROES-50, ROES-PH75, ROES-UV75, RO-90, RO-PH90, RO-PERM, RO-PUMP; iSpring RCC7, RCC7P, RCB3P, RCC7AK, RCC7P-AK, RCC7U, RCC1UP, RCC7AK-UV, RCC1UP-AK, RCC7D, WCC31, CT10, CKC1C, HC16, WCB32C; Geekpure RO5; Olympia Water Systems OROS-50, OROS-80, OROS-80-ALK. Whats included: This item includes three (3) O-Rings with "iFilters" branded packaging. Manufactured and warrantied against defect for one year from purchase date by iFilters. 3rd Party purchases are not warranted. "iFilters" is a registered trademark of iFilters.