Hello,

I bought one of these:

http://www.toolstation.com/shop/Stru.../sd2804/p96056

Like all fittings of that type, it has a black rubber seal around the
end. Under the seal is a rigid red circle of plastic. Is it important?
Does it keep the rubber seal in place? I ask because mine arrived
broken and I am wondering whether I can live without it or whether I
need to get a new one.

Thanks,
Stephen.