Can anyone advise me what material is used for the white, soft, (flimsy)
material used as a gasket which goes between the sight glass and a room
sealed heater heat exchanger?
The sight glass has got dirty, and I'd like to replace the gaskets if
possible. (They're rectangular with a circular aperture and there's two -
each side of the sight glass.)
[It's a Potterton Levante heater if this is important.]

Many thanks.

--
M Stewart
Milton Keynes, UK
http://www.megalith.freeserve.co.uk/oddimage.htm