What size bottom bracket do I need? What size seatpost do I have? What size bearings do I need for my headset? All valid questions for beginner bike mechanics and technical specialists alike – and all answered with the precision Digital Caliper. With accuracy to 0.01mm (0.0004″) and a 15cm (6″) capacity, this all-metal caliper is twice as accurate as our competitors and sets the benchmark for Imperial and Metric measurement.