I recently ordered a top sheet (high density polyurethane) for a box we made 4 inches by 196 inches long and 1/2 inch thick, this cost $60 (not including shipping, I picked it up in Denver). This is the materials and source that Keystone uses for their boxes and it is DOPE! We seshed the past two nights and it is as smooth as a double barrel rail. Contact Paul at the Denver location or myself if you have questions. Worth the money if you want a sick set up! I will try to get pics soon.