I tried one of the early Kaidomain ones. You have to unsolder the outer spring (or order the one without the spring, which then will not work well in a Surefire G2). If you don't get a good fit between the base of the dropin and the collar of the WE, you can either wrap the base in aluminum foil, or put a loop of 22-24 ga copper wire parallel to the axis of the body.