these things are awesome and I don't know why I didn't purchase them long ago. If you're anything like me and like to keep your glass nice and clean these rubber caps are worth their weight in gold, they make cleaning 100x's easier than before and they're at a highly affordable price point.
This tool makes cleaning a breeze quick and easy. Definitely recommend letting the caps fully dry between each clean. Thank you 420science for providing this great product.
I guess that these would do in a pinch to allow some interior cleaning, but a thorough soak in a cleaner like Smoke Soap does a far better job on all components, inside and out, with no risk of leakage.