I have one 16" Dial Barrel Gauge that will measure the 'Inside' Diameter of 10, 12 and 16 gauge Barrels and Chokes. It is new in the box. I will sell for $150.00 plus $20.00 Priority Shipping. Do you know what constriction you are shooting now ?? This is the easiest way to find out.-- Comes with simple instructions. PM me here.---------------Thank You !!