Apparently there are two types of kegs that use inserts similar to these. My Firestone / Racetrack kegs needed a insert shorter than this one that from what I can tell doesn't exist anymore. When this one didn't fit I held it with a pair of needle nose pliers and trimmed about 1/8" off the bottom. The cut is a bit rough so I heated an old kitchen knife and quickly melted the bottom smooth again. This step wasn't necessary for function but I figured it could help keep it more sanitary.