Post
by Kev888 » Sat Jun 24, 2017 9:26 am
That looks like a "bonded seal" washer. They work alone, no extra seal needed, and aren't considered disposable (some of the plain soft washers technically should be changed each use, though we tend not to).
That said, they can still be damaged or wear out and so may need replacing eventually. I can't quite work out if that is a split in the seal at the top (bottom picture). Also, the seal/rubber-bit is around their centre, so if the cylinder has a sloppier fit or more countersunk recess they may not seal as well as a plain soft washer.
Kev