4" Snail Lock Back Up Pad with Thick Foam Velcro

4" x 5/8" thick x 5/8-11 Thread  Plastic Back Up Pad with Tick Foam Velcro are made to be used with Velcro backed silicon carbide sandpaperThe 5/8" Thick foam gives plenty of cushion for the sandpaper to roll over the edges and inside bowls, etc when sanding.5/8-11 brass thread Center water hole for wet use.Can be used wet or dry.