Size Catcher - Bolt Head Measuring Tool - Both SAE & Metric Measurements - Comes w/Chain Instantly get an accurate measurement of the size of any nut or bolt head with this size catcher (also known as a bolt head measuring tool) Conveniently features both SAE (standard) and metric gradations on opposite sides Features an adjustable chain to take with you on the go, to put on a key chain or hang up in your shop SAE range measures 5/16-1" and metric range measures 8-25mm Dimensions: 3-2/5"L x 1-9/10"W (when enitrely opened) x 2/5"D. Product weighs 2 oz