a couple others also said mat, i have this one and its tough material and good cushion with ability to load bipod up properly

https://www.amazon.com/MidwayUSA-Competition-Shooting-Olive-Drab/dp/B00O7ZKZOK/ref=sr_1_3?ie=UTF8&qid=1527261382&sr=8-3&keywords=midway+shooting+mat