Vital PartsPack of 4 Silicone Tapered Plugs with Handle 41.3mm - 50mm, Easy Removal Plugs, Stoppers, High Temperature, Powder Coating, Masking, Silicone Bung, High Temp Masking, Rubber Plug

Had to return and get a different size (my fault) customer service fantastic. I've use this to plug the waste tank on my campervan and it holds all the water no problem. Ace

Good productUsed as emergency pipe stopper on plumbing

They are bungs - no issues