I second boomer. I found out the hard way (literally) that they need to be stored muzzle down or on their side. While I was away at school my only shotgun at the time stayed at home standing in the corner of a closet on its butt. Four years later, the weight of the gun compressed the recoil pad to the point of being a solid, inflexible, unforgiving chunk of rubber. It might as well have been made of wood. That is how I found out about the Limbsaver recoil pads which work very well, but that is another post. If you shoot your gun(s) as frequently as I do, I think a silicon sock is optional since they are cleaned on a regular basis but if they are going to sit untouched for a while, it is probably a good idea.