Need help quick... felpro rear main teflon seal question

This might see like a newbie question, but I'm in the middle of a clutch swap and I am installing a new rear main seal. I have done TONS of these in the past, but never with the felpro teflon lined one, its part number 2941. It came with a large plastic ring inside of the seal in the package. My question is do I toss it or use it? I hope I don't have to use it as I tried to slip it on and cracked it already. thanks!
Paul

Thanks Andy! I already have the rear main seal, flywheel, and clutch back in the car. For as tight as it was without the plastci, I know it had to right. thanks again!
Paul