My block is 3/4 thick, bolted to a 1" thick x 5 inches wide with 1/2" allen bolts..It's a T, with holes in one side for G38 size cranks and the other side for G62 size cranks..it fits in my Kurt vise on the mill table...Most lathe chucks are not good enough to check alignment within .001, so the block was the answer...It's about 12 years old.....