Used to size metric nuts or bolts. Has actual steel fasteners in the gauge for sizing the different diameter nuts and bolts. Check male and female threads 6-32 to 9/16" (UNC & UNF) coarse, medium and fine thread. Check male and female threads 4m to 12mm, various thread pitches. Handy ruler in inch and metric lengths. Check screw sizes from #0 to #14. 39" H x 3" W