These receivers are required to allow the attachment Prieferts wishbone carriage (CA04-2 or CA04-2WT) to your model S01, S0191 or S04 Priefert squeeze chute. Prieferts innovative wishbone carriage system is simply the easiest one-man chute loading system on the market and makes moving your squeeze chute a snap. The model S04 chute uses CRS04-2 receiver. Select the appropriate receiver and follow the simple instructions to mount it to your chute.