This Super-light Caliper/ruler Combination Is Easy To Use; Has A Locking Mechanism. Measures In Both Sae(inches) And Metric(millimeters); Up To 24" Or 610mm. The Minimum Inside Measure Can Start At 10mm (1cm).* Measures Inside And Outside * Uses Both Sae And Metric * Lighweight Aluminum * Handy Hanging Hole * Extra Long For Bigger Jobs