Tools4Boards HONE DUO Ski and Snowboard Diamond Stone (400 Grit Medium Two Sides), Black Matt Premium Swiss-made diamond sheet mounted on exceptionally flat precision die-cast aluminum alloy backer 400 Grit Medium Two Sides Extra thick 7/32" (5.5mm) backer dampens vibration and will not flex and roll over dulling the cutting surface of the ski or snowboard edge Backer dimensions: 4 3/4" (120mm) x 1" (24.5mm) Unique diamond cluster pattern lasts longer than conventional diamond sheet Black matt textured finish allows stone to be used wet and provides superior diamond adhesion