ADD-ON KIT M12x1.5 Big-Sert universal head bolt ONLY PROVIDE THE NECESSARY TOOLING TO CONVERT TO BIG-SERT You must have the original kit 4800. What is Included: Drill, Tap, Bushing, line pin, Inserts and dowels. Second repair after a failed coil style insert. Kit includes 10 inserts of  the P/n 52155  Extra head alignment dowel P/n 7225BS  &  J-42385-508BS   2 of each size included in the kit  Tool setup video here.