It's a clamp! And it's meant for pipe diameters of nearly 2.75 inches! You can just google the part number of this and any other Dynomax/Walker Exhaust clamps to find out the specifications for any clamps like this (or pipes) where AutoPartsWAY doesn't have the specification.The clamp was tossed into a cardboard box with both bolts. That's great. What sucks is that there is a putty compound taped to the clamp, and after traveling about the word, the bolts have a tendency to hit, dig into and spread the material all over the inside of the box. Quite the mess! - but this is for dirty, industrial manbeast work after all, right? I think threading the bolts through the clamp prior to shipping would fix this, but it'd probably push the cost up, so I'm quite alright with it. Will you be?