This cap was used on a pump we made from a 5 gallon bucket for our aquarium. It fits perfectly in a standard 5 gallon bucket and won't leak even when the pressure of a large 75 gallon tank forces water through the bucket. This saved us a lot of money ($200) on a good filter. The regular bucket lid that came with the plastic bucket leaked so we ordered a metal lid and it worked great! Highly recommended. We were also able to easily cut the lid and thread the tube through. Still no leak! The hinge closure is very strong and waterproof!