Granberg"s Blue Grit grinding stones provide hollow ground edges on Chainsaw chain, ripping chain and Hedge trimmers. Provided three to a pack, use of these stones will significantly lengthen the life of your saw. When used in conjunction with Granberg"s Dual-Sharp, they can produce sharper-than-new edges on hedge trimmers. For best results, use with Granberg"s G440 Kool-Grind lubrication stick.