Pentair 192323 O-Ring Replacement Pool/Spa D.E. Filter and Pump O-Ring replacement Fits Pentair FNS, Nautilus and Nautilus Plus pool and spa D.E. filter models NSP36, NSP48, NSP60, NSP72 Also fits Pentair Bermuda skimmers and Hydropump pool/spa pumps Circumference is 2.25 in. and thickness= 1.5cm.