Since both are so cheap I decided to try both Gorilla TG1 and Milton S921. Gorilla consistency shows 3 pounds lighter than Milton or other 3 calibers I already had so I returned it. Milton is definitely the best product. It's more accurate and has a deeper cup that fits over the valve stem, making installation much easier and giving good, quick readings. It's difficult to fit a gorilla square onto the valve stem, so half the time you end up with poor contact and even lower readings. Definitely take Milton.