Use these on my Sig 522 Pistol and they are great! I made the mistake of buying 4 of the 32 round ProMag ones based on good reviews but I do not like them at all! They have too much play in the receiver, are extremely heavy, and never keep the bolt open so I always dry fire it after the last round which is bad for a rim fire. With these the clear smoke is nice to have, gives an idea of how many rounds are left, and the follower is tall enough it keeps the bolt from closing after the last shot. It does not lock the bolt open, which is the gun design, but at least I can tell by the sound it didn't shut and I'm empty, also prevents dry firing. Overall very pleased with these Black dogs and this is as cheap as they were before the panic buying which in my mind deserves a 5 Star rating.

I bought these because I was hoping they would be lighter than the bulky ProMag since my Sig 522 is a pistol with metal upper & rails, after scope and accessories its rather heavy and difficult to stabilize and shoot offhand. These really help cut down on a few ounces and I have now bought a few more.