So you want to use your K&M mandrels in one of our neck turning tools. Or maybe you want to use one or those K&M mandrels in your Sinclair Neck turning tool. This little sleeve does just that. Simply drop the sleeve into your neck tool where the 3/8" shank mandrel goes, thread the mandrel locking screw into the through hole in the sleeve and install your K&M mandrel in the neck tool as normal.