I have a 36mm on mine, I made a huge difference in body roll. The best way to determine if its a 36mm is to measure the diameter, or you can use a digital caliper to measure it. Even putting the open end of a 36mm wrench on the bar works (should be snug fit if its a 36). If your trying to find one in a salvage yard look specifically for the Pontiac F bodies, they are far more likely to have the big bars then a Camaro. Pay close attention to cars with 16 inch wheels or look at RPO codes on car if label is present. The RPO's your looking for are either 1LE or WS6, both of which would have 36mm bars.