For my personal range I use 3/4" foam insulation board. The resulting holes aren't perfect, but you can hang targets quickly and easily with toothpicks and they last a long time...my 100yd one just split in half in the wind after 2 years of shooting, I'll get another 1-2 years out of the 200 and 300 yd backers. I'll take the increased life compared to plywood I used to use and ease of target hanging over the holes being perfect...I don't do much fussy enough to care about that anyways.