Commercial and military pilots use Evans Industries gel filled ear pads as they last up to five years, and must endure hot and cold temperature extremes as well as long term exposure to skin oil, an unexpectedly aggressive substance. These cushions use thermoplastic polyurethane cover over a foam pad, to give them the durability and toughness they require.
Snowmobile and motorcycle helmets take a lot of abuse. They can be left outside where they are exposed to extreme temperatures. The ear muff pad must be strong, impervious to substances such as skin oils, and stay soft and comfortable to wear for hours at a time. Thermoplastic polyurethane is the only material that will remain flexible and reliable under these conditions. Vinyl covered cushions become hard and brittle.