YOU WILL NEED A METRIC ALLEN WRENCH (M8) TO TIGHTEN THESE BOLTS. Here is a nice group of 5/16-18, coarse thread, grade 8, beautifully chromed allen bolts with a smooth head. This auction includes five (5) 1.5" bolts and five (5) 2" bolts. Also included are 5 flat washers and 5 lock washers.