TIME-SERT KITS HAVE BEEN TESTED AND APPROVED BY GENERAL MOTORS THERE IS NO OTHER COMPANY APPROVED FOR THESE REPAIRS IN ALUMINUM BLOCK The core drill included will allow a special 11.7mm length no flange insert to be installed deeper than the standard kit. The mechanic doing the repair will have to set the counterbore depth manually by hand. If a repair has been made before and this is the second repair, you must purchase the 1812 Core BS (Big Sert) kit which is over-sized. There are two sizes for the GM rocker arm repair, M8X1.25 and M10X1.5. Please measure the bolt for the correct size. This kit is for the M8 ROCKER ARM thread repair. AND IS NOT FOR THE M10 ROCKER ARM.