Time-sert repair kit tool RENTAL, size 5/16-18, coarse: kit includes the correct drill bit,a cutter, insert tap and installer & 2 short inserts for you to use. Comes with instructions. will allow you to fix carburetor studs in head, bolts in blocks, rear housing bolts. Included in the rental price is a core charge of $66.00 that you will get back, providing you return the kit minus the 2 inserts to us complete in good condition within 30 days. If you need more inserts, you can purchase them separately, they are available in the " tool rental & misc. page.