I used 3" PVC insulation, gray color. For my surfboard rack. It fits fairly good around the crossbars. I still have not come up with a good strap system to tie my surfboards down. Bungies seem ok but I'm still a bit uncomfortable with them since the smaller versions seem to pop out from the hook part. What do you guys use for straps and how do you attach them to the rack. Notice there is no loops or holes in the rack its self.