This is the system i'm pretty sure he has Tony :
The sealing ring is SBG5 in that diagram and is pretty generic throughout not just Volvo exhausts but many others as well.
If all else fails, the clamp rings can be removed by cutting the ends of the two pipes and joined using one of these :
https://www.ebay.co.uk/itm/Audi-100-...t/301941663929
I think 54mm is the right size, would be wise to measure first though! The clamp bolts need tightening evenly, a couple of turns at a time on each or the sleeve will distort and blow.
All that said, if the exhaust parts aren't rotten (Phil mentioned slight pitting on each so nothing to speak of really) a new sealing ring and some copper grease on the ring after cleaning the inside of the conical bits of pipe then progressively tighten the clamp bolts as it warms up usually sorts it.
