Review on Vented Fill Cap with 2-inch Base by Fill-Rite FRTCB by Raul Fabijan

Almost standard filler cap that fits over the top of a fuel drum. Without blocking. The lid has a moisture seal and is spring-loaded, so while it relieves pressure, it doesn't let in as much moisture as a lid without a seal. The threads are acceptable, but not the cleanest I've seen. So expect to use sealant when installing. Seems a reasonable price for what you get.