2 PCS Car Toilet Seal, 4" x 2.7" x 0.27" Highly Resilient Silicone Flush and Leakproof Round Gasket, OEM 385311658 Replacement Parts, Compatible with Dometic 300 310 320 Series RVs (Black)

These toilet rings fit the Dometic 300 toilet in our RV perfectly. Our RV toilet ball stopped holding water about two years in and gradually turned worse. To a point water would leaked down in minutes. We got these new sealing rings. Removed and cleaned up around the opening, and installed in minutes.Three things we did which helped. One is to smear silicone plumber grease on the ring. 2nd is to check for imprint THIS SIDE UP and follow. 3rd is to install the new seal with the toilet ball CLOSED. After the ring is installed, feel the edges and make sure it's tugged in with no ripples. With this new ring installed now our RV Dometic toilet can hold water for weeks without dried out. Very please with the minimum effort, huge improvement DIY items.

I got these as a replacement for my gasket ring in my Dometic toilet. The rubber seems nice and sturdy, flexible with the groove in the center that should fit just right. I will be replacing my gasket later however it is nice to have backups.