Agree all of the above. Certainly Laurie and Dave are excellent service technicians ; I do them too, although at the moment spares are a little hard to get, for me certainly. When cocked if you look into the action, you will hopefully see a nylon seal [ actually a buffer] if its not there, it has already disintegrated and been shot out of the barrel; not uncommon on older FWB guns. that's a replacement for sure, as has been said if it's white it's likely to fail any time; blue or green are newer respectively; red is almost certainly a Knibbs generic one. Same applies to breech seal, easy to see; white needs changing, blue might be ok, green is the latest so could be ok, red again is Knibbs. Hope this helps