At the advice of a gun friend I bought a Super Safety for for an AR-15 from Fudd Arms.... Palmetto State Armory had an AR lower on sale and I went and picked one up just to have this on.... (Only took about 45 minutes to do the 4473 but that is a different story). So I put this on the PSA lower and could not get the trigger to trip on either of my AR uppers... still don't know why... So I decided to just take it off the PSA lower and put the original factory safety and trigger back on... I did this and it will work on either of the uppers in it's original condition... then I figured what the heck, might as well try the Super Safety on one of the other lowers... decided on my first AR a DPMS I got almost 20 years ago... it acts like it is gonna work... will find out next weekend... but talk about a pain to deal with.... I know these things are supposed to be easy to take down and work on but it seems at 68 years old I have become clumsy and can't see worth a dern.... 2 hours at least of absolute tedium... and cussing like a drunk sailor at times....