Cork is an excellent material to use under the rear bag especially if you are shooting off a hard surface eg concrete or wooden benches.
It is a dense energy absorbing material which will not react or move when the gun recoils.
Great if you need to add a bit of height to your rear bag
Designed to fit the Edgewood Original Rear Bag
Measures 22x17cm (at the widest points) x 1cm thick
Can be trimmed down more if you need.