CZTD99, for 18 piece set. NF 6-40 #33 to 1/2"-20, 29/64" tap and drill index. Holds National Fine sizes: 6-40 tap #33 drill, 8-36 tap #29 drill, 10-24 tap #25 drill, 10-32 tap #21 drill, 1/4-28 tap #3 drill, 5/16-24 tap #I drill, 3/8-24 tap Q drill, 7/16-20 tap 25/64" drill, 1/2-20 tap 29/64" drill. All-steel reamer cases. Each storage hole is precisely sized for accurate, quick tool selection. Raised embossed lettering for permanent identification. Corrosion-resistant, epoxy baked-on coating. Secure, snap-lock steel cover. Rugged, heavy gauge all–steel case.