Great but falls short if you have a mil-spec tube - FAB Defense GLSHOCKCP Recoil-Reducing M4/M16 Buttstock

Overall I liked it a lot, for these reasons: (1) Was able to get my cheek weld dialed in perfectly with the adjustable cheek riser. (2) My Diamondback kicks like a mule and I was pleasantly surprised how well the recoil reduction works, made a big difference. However the so-called Unique Patented "Anti-Rattle" Mechanism is not working. The stock rattles pretty badly and it's real annoying, especially when the Anti-Rattle Mechanism is supposed to prevent rattle movement. Found out that this stock is "universal" so it's supposedly made for both Commercial and Mil-Spec, unlike how these stocks are shown on OP where it looks like you can order either a mil-spec or commercial the way they are listed. Because they are "universal", they really are made for commercial tubes but "will work" on a mil-spec. As a result it will not fit snugly enough on a mil-spec tube to engage the so called Unique Patented "Anti-Rattle" Mechanism so it functions as described. Pretty bummed out because I liked the stock but cannot stand the rattle. FAB Defense should make this stock for both types of tubes instead of this "universal" garbage which it really is not, this is actually a commercial tube buttstock because the "Anti-Rattle" Mechanism does not work on a mil-spec tube which means the stock is NOT a mil-spec stock. It if was then all of the features described would function on a mil-spec tube and again they do not. I cannot recommend this stock to anyone with a mil-spec tube.

Also irritated with how long Optics Planet shipping time has been lately, they use to be surprisingly speedy with delivery averaging around a week. Lately it's been averaging 2+ weeks. Which makes it even more irritating if you waited for 2 weeks for a part that gets here and then does not function as described and you have to send it back and wait another 2 weeks for a replacement part that will actually fit properly and WILL function as described. Not sure what's going on but I suspect they switched carriers and they are pretty lousy on timely delivery.