This is a picture of a brick, not a great picture but, none the less, a picture. Someone might suggest this looks a lot like a Marlin 1895G factory recoil pad,
but it can't be, because it doesn't flex, twist, compress, or even bounce very high when tossed to the ground.
Hiding within those dark recesses is a .600" vertical stiffening rib. It runs right down the middle of the pad, no doubt to insure those side compression voids
never flatten in use and lose their original shape. The pad's not made of Sorbothane, it could be recycled off- the-road radial tire rubber, but I don't believe
tires are made from compound this hard.