automagsUK.com: Classic and RT Tech Guide

The X valve is the exact same thing as the RTP valve, the only difference is most of it is made of 7700 grade aluminum rather than stainless steel. This saves you 3oz. If you slip valve into your Automag or Minimag, you've pretty much turned it into an RTP (It keeps the Auto/Mini on/off pin length tolerance though(.750")). The Xvalve comes with the Level 10 kit installed(see Level 10 section)

If you purchase this valve for the Emag, you'll need to switch On/Off pins(Emag - .712") and use the Quad o'ring to make it work properly(see section About the Emag and Xmag Valve).

Remember when purchasing a new X valve that since it's new you will need to heavily oil it as well as break it in. It's also a good idea to break in the spring pack by turning it all the way in and then back it out again.