Precise and easy-to-use internal and external thread identifiers for nuts and bolts. Steel identifiers are strung on a wire lanyard. Permanent, easy-to-read size markings are laser etched into each stand off. Shatterproof, color-coded polypropylene gauge divider beads allow recognition between inch and metric strands. SPI Standard Thread Detective Screw Pitch Gage: Inch & Metric, 13 to 32 TPI. Inch Sizes: 6-32, 8-32, 10-24, 10-32, 1/4-20, 1/4-28, 5/16-18, 5/16-24, 3/8-16, 3/8-24, 7/16-14, 7/16-20, 1/2-13, 1/2-20. Metric sizes: M4x0.7, M5x0.8, M6x1.0, M8x1.25, M10x1.0, M10x1.25, M10x1.50x M12x1.25, M12x1.50, M12x1.75.