Gehmann - Rear Iris Default:Twin Polariser (551) this stock has it

this stock has it

AHG9736     M18 - 2

you need the mounting rings to fit this diameter

This item is tubular shaped and made from liquid plastic which is hard enough to protect and soft enough not to scratch or damage the bolt itself

Gehmann - Rear Iris Default:Twin Polariser (551) this stock has it(#PH510) Gehmann Rear Iris Adjustment range 0. 5mm 3. 0mm. Thread size suits Parker Hale or Redfield. (#550) Gehmann Rear Iris twin polariser, Adjustment range 0. 5mm 3. 0mm. Thread size 9. 5mm. (#551) Gehmann rearsight iris with twin polarisers and 1. 5x diopter, incorporates #550. Adjustment range 0. 5 3. 0mm. Thread size 9. 5mm (#566) Incorporates the patented 510 iris, Adjustable over a wider range of 0. 5 3. 0mm. Filters are of the highest