The Z body mag that i was recently given has a classic valve in it but has an on/off that i have never seen, It is not an rt on/off or a ULT but it does have a smaller diameter pin than the classic on/off and gives the classic a substantially lighter trigger pull. Have any of you ever seen this before? oh and it does use two o rings on the bottom of the on/off, only the smaller one is on it in the pic, the other is still in the bottom of the valve