The General Tools 3in. Digital Fractional Caliper is a carbon fiber caliper that brings you 3 universal systems of measurement, making it an equally practical choice for both professional and do-it-yourselfer projects. High-contrast digital display easily switches between inches, millimeters and fractions, with guaranteed accuracy to 0.001in. Plus, the lightweight, carbon fiber construction delivers accurate readings of inside, outside and step measurements. This 3in caliper fits conveniently into your pocket for working in the field.