When shooting off of barricades, it's desirable to have some kind of padding between the stock and the barricade surface, otherwise the rifle will jump during recoil, making it hard for the shooter to spot his own shots. Short Action Precision has come out with a barricade bag that straps to your rifle and uses a filler that is as light as a feather. The weight of this bag is very impressive. It makes your typical plastic pellet filled bean bag feel like a brick. It has a quick release buckle that allows the bag to be released and used as a rear bag when transitioning to prone. It also has a tether strap that can be fastened to a sling clip (not included) to secure the bag to the rifle when not in use. This is usually not desirable with bags filled with pellets as the weight throws off the balance of the rifle. There is a rubberized pad on the bottom that prevents the bag from slipping. All of the high end gear seems to be using this rubber material. It was also on many wrist coaches.
Accu-Shot, the makers of the Atlas Bipod, have come up with a product that fullfills the same need, but this one is for AR shooters. The SILO clamps the the pocatinni rail to provide a soft interface on barricades. It also has a knurled front end so that it can be pressed against the side of a ledge/hole.
The story behind the SILO:
The SILO was conceived on a crop control hunt where an actual grain silo was used as a blind. One shooter, an active SOF community member was using a bean bag strapped to his Atlas bipod legs to rest his rifle on the silo window ledge. This was a bulky solution to providing a “soft” interface between the rifle and concrete ledge. As the hunt continued the conversation turned to gear, which led to the SILO.