I fitted a translucent orange one which I think came from TR Robb. My Lightning (although hardly used) seemed to have a larger than normal gap between the breech face and cylinder so even a new standard breech seal didn’t completely stop air leakage.

The orange one needed a lot of fettling to get the thickness bob on (rubbing on wet & dry) but when fitted the seal is fantastic and shows no signs of wear after several thousand shots.

Cheers
Greg