Some people were asking about recoil rating and suitable calibers.
These units were TESTED to withstand up to 600g acceleration.
This means they will hold on a rifle of any practical caliber.
They work fine on .308, springer air guns, and anything in between.
You'd have to be more careful with .500 Nitro Express, but we don't think many people would be using it with .500NE.
EDIT: Be careful with eye relief on larger calibers, because all thermal and digital scopes have shorter eye relief than conventional optics.