How to choose the right clamp?

EXHAUST CLAMPS come in a variety of styles, designed to be used in conjunction with different types of pipe connections. Twenty years ago, automotive service shops could often settle on a single, standard-duty exhaust clamp as a one-size-fits-all solution; however, newer exhaust systems have rendered this practice dated and ineffective. Treating all exhaust clamps as interchangeable can lead to safety concerns and other issues. Using the wrong style of clamp on modern vehicles can impact things like:
Sealability – The wrong clamp can create a loose exhaust seal, resulting in poor fuel economy, high emissions and – in some cases – the release of dangerous exhaust fumes into the cabin. 
Durability – Some clamps provide longer service life than others, and using the wrong one can easily turn a muffler into a road hazard. 
Serviceability – Clamps designed to be removable allow vehicle components near the muffler to be serviced without damaging the vehicle’s exhaust system.