Generic O-ring Ultimax.  1/2 inch innder diameter.

X-section is 3/32 inches.  Ref number O-39.

This oring used in many booster pumps, cleaner pumps, filter pumps and pool pumps including:

ABS 2", Acura Magnaflow, Booster Pump, Champion 56-Frame Model CHAMPE, Champion 56-Frame Model CHAMPS, Cygnet Series, Dirtbag, EX2 Spa Pump 48-Frame & 56-Frame, IntelliPro VS 3050 High Performance, Jacuzzi Bracketless 48 Frame 60Hz, J-200, Jacuzzi Bracketless 48 Frame 60Hz, J-300, Jacuzzi Bracketless 56 Frame 60Hz, J-300, Jacuzzi Bracketless 56 Frame 60Hz, J-400, Jacuzzi Bracketless 56 Frame 60Hz, J-LX, Jacuzzi Bracketless 56 Frame 60Hz, J-LXL, Jacuzzi CFR 100, Jacuzzi CFR 150, Jacuzzi CFR 50, Jacuzzi CFR 75, Jacuzzi CFR Series Inline 1-1/2", Jacuzzi Earthworks EW100, Jacuzzi Earthworks EW125, Jacuzzi Earthworks EW150, Jacuzzi Earthworks EW75, Jacuzzi Fixed Bracket 48 Frame 60Hz, J-200, Jacuzzi Fixed Bracket 48 Frame 60Hz, J-300, Jacuzzi L Pump, Jacuzzi LC Pump, Jacuzzi LCM Pump, Jacuzzi LCU Pump, Jacuzzi LCUN2 Pump, Jacuzzi LH Model Pump, Jacuzzi LPC Model Pump, Jacuzzi LPH Model Pump, Jacuzzi LR Model Pump, Jacuzzi LR25 Model Pump, Jacuzzi LR3 Model Pump, Jacuzzi LR6 Model Pump, Jacuzzi LR9 Model Pump, Jacuzzi LT Pump, Jacuzzi LTC Pump, Jacuzzi LTCU Pump, Jacuzzi LTH Model Pump, Jacuzzi LTPH Model Pump, Jacuzzi LX Pump, Jacuzzi Magnum Force Pump, Jacuzzi Magnum Plus Pump, Jacuzzi PH Model Pumps, Jacuzzi Piranha "A" Pump, Jacuzzi RC Model Pump, Jacuzzi Ring-Lok P Model Pumps, Jacuzzi Ring-Lok PC Model Pumps, Jacuzzi Ring-Lok R Model Pumps, Jacuzzi Ring-Lok UP Model Pumps, Jacuzzi SLPH Model Pumps, Jacuzzi SLTPH Model Pumps, Jacuzzi TC-300, Jacuzzi TC-450, Jacuzzi TC-600, Jacuzzi ULCU Pump, Jacuzzi ULTCU Pump, Jacuzzi UPH Model Pumps, Legend II - LX2000, Max-E-Pro Series, MFM 15, Ortega 2 Port 90 Deg CPVC, Ortega 2 Port Straight-thru, Ortega 3 Port CPVC, Posi-Flo II Model PTM135, Premier Spring Water 225 MK2 Series Pump, Sonfarrel/Martec IC Series Inline, Sonfarrel/Martec Master Side Discharge, Sonfarrel/Martec TL Serie Above Ground, Sonfarrel/Martec TS Series Inline, StaRite, Supreme 48-Frame Above Ground Pump, SVL56 Pump, Vico Ultima, Vico Ultimax, Viper 56-Frame 2-1/2" Spa Pump, Workman 48-Frame Above Ground Pump.