This is a 4 Inch O-Ring designed to replace Anthony NS 4 Inch Pump Lid O-Ring. The outside diameter is 4.5 inches.
This after market o-ring is identical to these part numbers: Doughboy 308-1004 H&L Pot O-ring, Jacuzzi 47–0347-07R Gyromat O-Ring, PacFab/Purex NS Eastside H&L Trap O-ring, Swimquip NS Old Pump 4 inch Lid, Aladdin O-14, and SSC O-2240.
This o-ring has been manufactured in accordance with OEM specifications and are designed to meet or exceed specifications.