FOR RS AERO ONLY:

The Selden Bullseye Medium S/S Lined (508-604) has been superseded by the RS Aero Mast Top Bullseye Mk2 (AER-SP-915) and  RS Aero Mast Top Bullseye Mk2 Backing Plate (AER-SP-916). Button Head Machine Screw M5 x 20 (FIX-B5-B20) is the required fixing.