AP one leaks too easily.. The apeks one works better but needs routine rebuilds.. The most reliable one I have found are those sold by Oxycheq.. They have two versions. The original version that head a heavy barrel (a bit tight when used with the AP adv) and the slimline version..

another point to note the oxycheq version (manufactured by mj) works in a more logical manner, the isolator slid towards the device allows gas flow (think connect to source), operated away from desitination device cuts off gas flow (thing break connection)