zeroscore,

I got my FWB perspex inserts from Nikkonos on BayOfFlea.

I now use Centra High End glass elements - these screw directly in the FWB tunnel : I use them on my FWB300 (not 'S') and 300SU, and they work a treat :

https://www.intershoot.co.uk/acatalo...lement-48.html

There is also a chappie here on 'BBS - harvey_s, that makes custom perspex sight elements to order.

Have fun

Best regards

Russ