Made of high grade alloy steel, hardened and ground from stabilized stock. All are 6" long and 1/8" thick. All are within .0006" parallelism. Hardness 50-54HRC. Here is what is included in the set: 1 PAIR 1/8X1/2X6” W, 13/64” HOLE 1 PAIR 1/8X5/8X6” W, 1/4” HOLE 1 PAIR 1/8X3/4X6” W, 1/16” HOLE 1 PAIR 1/8X7/8X6” W , 5/16” HOLE 1 PAIR 1/8X1X6” W, 5/16” HOLE 1 PAIR 1/8X1-1/8X6” , 1/8” HOLE 1 PAIR 1/8X1-1/4X6” W, 3/8” HOLE 1 PAIR 1/8X1-3/8X6” W, 3/8” HOLE 1 PAIR 1/8X1-1/2X6” W, 1/2” HOLE 1 PAIR 1/8X1-5/8X6” W, 1/2” HOLE ACCURACY 0.0002” PARALLELISM IN HEIGHT PAIRED 0.0002” IN HEIGHT