My boys love their metal cup water bottles. Unfortunately I left the rubber washers on top of the cage, while cleaning the rest of the bottle, and the washers were chewed on. Luckily Rentacoop sells replacement parts so the bottles are back in order and are good as new.
I use the silicone washers and wing nuts with the rent-a-coop chicken nipples and automatic fill chick cup waterer(they're included with the chick waterers) to insure a drip proof seal when used with a thin wall plastic water container. I used them with a large coffee container in my brooder box (only 8 chicks) and no drips!
I actually didn't need replacements (the cups come with one) but got some extras just in case. Have never had a leak either unless the cup is touching something underneath it, but that is operator error. Lol Great products from this company!