This is a pellet backstop with stainless steel on the backside ( just under 1/16" thick) . I made a small box to fit inside of this filled with rubber mulch (see picture) ,it worked fine but if I was going to do it again I'd build one out of a 2x6 frame work just to be able to add more mulch. I will include a bag of rubber mulch also. Will sell for $25. LOCAL PICKUP ONLY Ridgefield Wa. area. Inside opening is 281/2" wide x 161/2" tall x 9" deep. 
