This breech seal washer fits most models of BSA spring air rifles:
BSA Meteor (Except MK7)
BSA Supersport
BSA Lightning inc GRT and XL models
BSA Challenger
BSA Mercury
BSA Spitfire
BSA Scorpion Pistol
BSA 635 Magnum

This is the seal that goes in the end of the barrel.

Now only available to us in black.