The Deep Well ThreadChasers are a perfect companion to any Irwin Hanson Tap and Die set. They are made to clean and repair exposed studs and bolts. These are available in 14 different sizes in 4 different set configurations. This set includes the following: 3/8-24 NF, 9/16-18 NF, 7/16-20 NF, 5/8-18 NF and 1/2-20 NF.