Rubber sealant/Non-Hardening Putty

[Woody3]

I've got an outdoor light that has a perished rubber seal around the glass shade, which I'd like to renew.

I can't seem to find the correct seal for love nor money, but seem to recall that I have used a putty like substance that was always reworkable, but worked perfectly as a seal. Can't for the life of me remember what it is called though. Any ideas?

[Woody3]

Plumbers Mait looks to be the stuff.

Thanks chaps.