Designed for use with the RCBS Lube-A-Matic Bullet Sizer/Lubricator, the Sizer Die casts lead bullets to the proper diameter and adds bullet lube to grease grooves. It's precision-honed to 0.0005-inch tolerance. Use with the RCBS Lube-A-Matic Bullet Sizer/Lubricator Cast lead bullets to the proper diameter and add bullet lube Accurate to within 0.0005 inches