Well I suppose you could reuse it. But why wouldn't you just replace it all when your in there? Stainless ring. Carbon ring and bellows boot. Using oem stuff! Then your not getting it all back together and still experiencing problems. The parts arnt that much when it comes to the headaches you would have and frustrations when you get back out to the water and it's still got some cavitation.
I replaced my wear rings, carbon ring, stainless ring, bellows boots. On both of my engines on my sportster 1800 and I don't have any cavitation at all anymore!!! Well worth the money!!