Simply push the gauge in the muzzle of the gun and when the segment fits the bore perfectly. Read of the gauge the amount of choke of each barrel.

This high quality shooting accessory is essential when buying a fixed choke pre-owned gun, As the choke stamps may not correspond to the amount of choke in the bore I.

E sometimes choke is bored out by a gun smith and they do not always re-stamp the new choke on the barrels As for multi choke guns the choke stamps can wear off etc. and some people get confused as to ascertain what choke tube is what, simple to do with this gauge.

BORE (OPEN) ~ True cylinder ~ 0.00" ~ Cylinder (on 12g gauge only).

IMP ~ Improved cylinder ~ 0.05" ~ Skeet 1/4 ~ Quarter choke ~ 0.10" ~ Improved Cylinder 1/2 ~ Half choke ~ 0.20" ~ Modified 3/4 ~ Three quarter choke ~ 0.25" ~ Improved Modified FULL ~ Full choke ~ 0.35" ~ Full