Advantage: 1 inch 1. Small volume, larger flow rate that is up to 150 lpm. 2. Fluid pressure can reach 8 bar. 3. The epoxy coating of air valve. 4. Reliable air commuting valve   RD series air operated diaphragm pumps' sizes vary from 3/8 to 4 inch inlet/outlet, The pump body is made of various material, including PP, acetal, PVDF, Al, SST, CI, etc, which with high quality and good-looking appearance, is very similar to Graco's, but much cheaper than it.