The StudioPro Space Saver adapter bat is 100% compatible with the Wonderbat system. This bat allows you to throw multiple small bowls and cups in one sitting and save you lots of shelf space in your studio. 1/2" thick exterior grade MDF. Warp resistant. The through-hole rubber grommets ensure a secure fit on your wheel head and can be used on both sides. This feature further prevents warping over time.