CZTD18, for 18 piece set. 6-32 #36 to 1/2"-13 27/64" tap and drill index. Holds National Coarse sizes: 6-32 tap #36 drill, 8-32 tap #29 drill, 10-24 tap #25 drill, 10-32 tap #21 drill, 1/4-20 tap #7 drill, 5/16-18 tap #F drill, 3/8-16 tap #5/16 drill, 7/16-14 tap #U drill, 1/2-13 tap #27/64 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.