This is a air inlet/bonnet for 1 1/4 - 1 1/2" Apollo/Conbraco 4V Series pressure vacuum breaker (PVB) backflow preventers. This is a direct replacement for your broken or failed air inlet assembly. This part simply threads into the device body. Do not overtighten. Genuine Apollo parts, made in U.S.A. A seat removal tool is needed to remove the seat.