This OEM unloader bolt is the lower brass bolt on the side of the pump that holds the unloader assembly to the pump and is the bolt that allows the water to enter the pump. Below is a listing of the unloaders this bolt fits. If you have any other questions or are unsure if this bolt will fit your unloader, please contact us through eBay. We are a full service pressure washer repair shop and an authorized A.R. dealer. Unloaders this bolt will fit:AR2973AR2943AR2944AR2945AR2946AR2947AR2968AR2973AR20821AR21036AR21158AR20888AR21037AR21038AR20890AR21039AR21040