This is a top quality gauge for checking size and thread pitch of screws, bolts & nuts. Works with fractional (standard) or metric screws & bolts. fractional screw/bolt size range: (#4 to 1") metric screw/bolt size range: (3mm to 22mm) standard lengths up to 7" and metric lengths up to 180mm. fractional nuts from #6 to 5/8". Made of 1/4" thick hard very durable plastic. It's 8-3/4" long and 3-1/4" wide.