Thread checker for nuts and bolts 23 inch 21 metric portable size identifier1、Comprehensive Set: You will receive 44 nut and bolt thread checkers in both inch and metric sizes to cover a wide range of applications. 2、Narrow Space Application: Our thread checkers are perfect fit for sizes checks in tricky and narrow areas, ideal for tight spaces where traditional meters may not fit. 3、Metal: Made from premium metal, thread checker gauge is designed to withstand the impact of daily use, perform reliably for a long time without wear or damage. 4、23 Inch Size: Blue inch size includes 1‑12,1‑8,3/4‑16, 3/4‑10, 5/8‑18, 5/8‑11, 9/16‑18, 9/16‑12, 1/2‑20, 1/2‑13, 7/16‑20, 7/16‑14, 3/8‑24, 3/8‑16, 5/16‑24, 5/16‑18, 1/4‑28, 1/4‑20, 10‑32, 10‑24, 8‑32, 6‑40, 6‑32. 5、21 Metric Size: Red metric size includes M3‑0.5, M4‑0.7, M5‑0.8, M6‑1.0, M7‑1.0, M8‑1.0, M8‑1.25, M10‑1.0, M10‑1.25, M10‑1.5, M12‑1.25, M12‑1.5, M12‑1.75, M14‑1.5, M14‑2.0,M16‑1.5, M16‑2.0, M20‑1.5, M20‑2.5, M24‑2.0, M24‑3.0.