Time-Sert 4001 GMC and Chevy M11x2.0mm head bolt thread repair kit. Note this kit is for GM straight in-line 6 cylinder LL8 Metric 11 x 2.0 mm, used primarily on 2002,2003-2004 GMC Envoy and 2002,2003-2004 Trail Blazer. This kit includes ten of the 112030 30mm inserts - 20 are needed for the entire block. See below in "related" for the link to more inserts. 

 

 Printable Time Sert 4001 Instructions

 

Timesert is recommended by leading automotive manufacturers.