Swix designed the Gummi Stone to remove nasty micro burrs that result after you sharpen your edges. Simply rub the Gummi Stone along the entire length of your ski or board's edge for a smooth finish. Or, just detune your tips and tails, which will reduce the chances of catching an edge, but will keep your side edges ultra-sharp for carving. - Grey stone is soft and works well for detuning tips and tails - Red stone is for polishing and light to medium edge clean up; can be used after filing to remove micro burrs. - White stone is for medium to heavy edge clean-up - Blue stone is extra hard for heavily burred edges ABOUT SWIX Drizzle. Wind. Sweat. Mud. SWIX is for everyone who loves training outdoors, in all conditions. Since 1946, SWIX has been testing and developing products for Nordic conditions, and knows what it takes to be the best – and to look good doing it. We call this SWIXFACTOR. - INSPIRED BY DREAMS