581-22 M.22 spirit level

M.22 medium-to-slow bubble that runs through twin markers
Internal M.18 thread for attaching a lens, filter screen or anti-glare tube (1. image) - accepts 558 direct
Screws into the foresight and is held in place by a lock collar - a C-spanner is provided to lock it in position
Once in position on the rifle whatever angle of cant you normally use can be set by simply rotating the whole bubble on it`s ratchet system
A friction collar holds your setting without need of more tools
Laser engraved degrees marked for reference