2 in 1- Metal Bubble Counter & Check Valve 2 in 1-Metal Bubble Counter & Check Valve Spring Check Valve Check Valve Stainless Check Valve 2 in 1 CO2 Bubble Counter + Check Valve CO2 Bubble Counter + Check Valve Vertical 3 in 1 CO2 Diffuser S 3 in 1 Compact V CO2 Diffuser S 3 in 1 Compact V CO2 Diffuser M 3 in 1 Compact V CO2 Diffuser L CO2 Check Valve (Black)