I tried to carefully drive them into my trailer drums but they were big enough that they were quite difficult to install. Luckily I'm a hobbyist so I found a piece of pipe I could cut to length to make it smaller to just fit over the lid. I welded a flat bar I had on the other end and was able to install the new caps. They have an installer available on ebay and other trailer parts sites. But it's another $20+ dollars and a few days to wait for them.