Use this nozzle selection guide and choose your orifice size based on the flow (gpm) and pressure (psi) of your washer

1 GPM - 5 HP

ST-1500 Spec Sheet

Complete kit

The 2-1/4"castor is comes with a mounting bracket and fits the FL-CR 520 model

Comet LWS3525S HM 24mm Solid Shaft 1750rpm 2500psi 3.5gpm 6301.1203.00 features_4-to-10-inch-pipe Use this nozzle selection guide6301120300 Comet LWS3525S HM 24mm Solid Shaft 1750rpm 2500psi 3. 5gpm Product Specs: Shaft Size (Diameter): 24mm Shaft Style: Solid Shaft RPMs: 1750 Inlet Connection: 1 2" FBSP Outlet Connection: 3 8" FBSP Pump Head: Brass or Stainless Steel Oil Capacity: 11 fl oz Weight: 13. 4 lbs Max Temperature: 140 F Warranty: 5 Years Features: Forged Bronze Connecting Rods Hardened Stainless Steel Piston Guides High Efficiency Stainless Steel Check Valves