All our new foresight irises come with a small mark between the two limit-of-adjustment marks (1) accept thread adaptors
The flat face of the iris can be unscrewed (2) and an adaptor inserted (3) for use of other accessories (4)
5018 is for our M.18 & M.17 irises to use lenses, screens, levels or anti-glare tubes
5022 is for M.22 foresights