Multi-step reamers feature 3-flat shanks to reduce slippage in the chuck. Shanks are 3/8”. Reamers are made from high quality M2 High Speed Steel (HSS). Black oxide surface treatment increases wear resistance. Enlarge existing holes in steel to a new, larger diameter. Can ream up to 1/2” thick steel plate. Realign badly misaligned holes to allow a fastener to enter through.