Below is a general manufacturer product group description. Please note the information below is not item specific. Item specifics are above in product details.

Why do you need exhaust hangers?
When new, OEM rubber exhaust hangers are fine for the stock exhaust system. But they simply don’t hold up or perform well in performance applications. Over time rubber breaks down and increases the amount of exhaust system movement. This excessive movement can damage the exhaust system as well as allow the hot tip to contact the bumper. PERRIN Polyurethane exhaust hangers are extra stiff to help keep your exhaust system in place, away from your bumper and other undercarriage parts. Most clients can install a set of hangers in less than 30 minutes with simple hand tools!
Construction
The PERRIN Polyurethane hangers are made from a special blend of polyurethane to withstand the temperature of high performance exhaust systems. In all kinds of conditions, from hot runs on a dyno, to freezing winter temps, the PERRIN exhaust hangers will outlast and outperform the stock hangers.
Stiffness
The stock rubber hangers are rated at a low durometer hardness of 55a. PERRIN hangers are rated at 75a to keep your exhaust under control with no additional NVH (Noise Vibration Harshness) to your car.