I measure for the container and cut the Ram bar base, I left about a half inch where it still curves over the Bed rail. other than the tiny gap that I have seen with the ones that did it with the Retrax mine needed a little more trimming at the canister because the Truck Cover USA has a top plate that has plastic trim, so it cut it back from the tubes of the Ram bar. I was told by Truck Cover it was not going to work, and I didn't want to spend another 2k when I knew I could mak it work.