This 2 to 4 Inch First Check Poppet Assembly Can be Used on The Deringer 40 (Rp) And 50 (Rpda-Ii) Models. They Are Designed For Sizes 2, 2 ½, 3 And 4 Inch And Comes Pre-Assembled From The Factory Ready For Installation. The True Seal(Tm) Check Valve Was Designed to Incorporate a Poppet Only Motion During The Check Stroke And is Used Exclusively on The First Check Assembly on The Deringer RP And Rpda Models. This Design Allows a More Consistent Pressure Loss Across The Check Valve Which Helps Maintain a Steady And Continual Closure of The Relief Valve. | Ames-Deringer | BD-4300