The ones that hold 9 suck donkey balls......I prefer the Beartooth Stock Guard, made from neoprene, not elastic. They hold six rounds and stay put. They're so damn hard to put on, it's easier to pull the barreled action and slide it on from the front. I run them on everything.

They have redesigned them, so I haven't tried the new versions yet.

[Linked Image from i.imgur.com]