This is a very well made Bipod that is adjustable to fit barrels from 11-19mm in diameter however as i mentioned you would have to file down the top clamp slightly to allow it to fit most underlever guns.
The barrel clamp is lined with rubber to protect the guns Blueing and to provide extra grip, the lower part is adjusted to fit various size barrels using a thumbwheel.
The ade locked in the up or down position and can be adjusted to vary the Bi-Pods height between 9" and 12". they also havehard rubber feet fixed to them.
With all metal construction this is a well made Bi-pod that i would strongly recommend for all break barrel air guns.