Exhaust Heat Sleeving lagging is a type of insulation material that is designed to protect exhaust systems from heat damage. It is typically made from high-temperature resistant materials such as fiberglass, ceramic, or basalt fibers, and is wrapped around the exhaust pipes to reduce the amount of heat that is radiated from the pipes. 

This can help to improve the performance of the exhaust system, reduce the risk of heat-related damage to other components, and increase the overall lifespan of the system.