O-Ring bulkhead replacement * Fits Pentair FNS and FNS Plus pool/spa D.E. filter models FNSP 24, FNSP 36, FNSP 48, FNSP 60 * Also fits Pentair Nautilus and Nautilus Plus pool D.E. filters models NSP36, NSP48, NSP60, NSP72 * Also compatible with Pentair Clean & Clear Plus cartridge filter models CCP240, CCP3201, CCP4201, CCP5201 * FNS plus made of 2-137 buna N 70 shore