underground drainage part 2

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Stephen saying something like:

Do you mean a ring underneath the rubber, so that the rubber is grooved onto it? A ring of plastic to retain the rubber seal is an improvement, but plenty were/are made without it, so I wouldn't worry. Once it's in place it remains where it's put, just the red ring would help keep the rubber more securely located as you push it in / slide it out.

Yes

I don't know what the purpose of it is.

the rubber

A piece of red plastic was sticking out from under the rubber seal, so I pulled it out to see what it was and it was a broken red circle. The hopper seems to fit snuggly without the red plastic present and I tested it with a bucket of water and there are no leaks, so I am hoping it will be fine without it.

I notice some plastic compression fittings for 32 and 40 mm pipe sometimes have rigid washers next to their rubber seals and yet other makes do not. I guess this is a similar thing?

Thanks for your reassurance.