I've used a few of these and they're great. I also tried Leviton and Leviton is not that reliable. It also has a gasket properly cut to fit a 50A 125/250V locking socket, these covers are designed to fit. The seal also has an adhesive backing to keep it in place when attaching the lid. The Leviton has a non-stick seal on the back and is not properly cut for containers. Shown is a Leviton seal below and a Marinco seal above. I had to cut the Leviton gasket to fit the outlet. The white paper on the Marinco is just a self-adhesive protective film that you peel off before installation.