Yes, you can completely open our SCUBA cylinder valves and eliminate the archaic quarter-turn-back practice you probably learned in your open-water class. All SCUBA cylinder valves from Dive Gear Express are modern designs that protect both the valve stem seal and the valve seat when fully opened; the valves are not prone to leaking or sticking open. The dive industry is moving away from the quarter-turn-back practice because it has been proven to cause dive accidents. The Alert Diver article titled Old Habits Die Hard has a detailed explanation from DAN.