The Grease Box™ is designed to be low impact and blend cosmetically with exhaust systems. The unique enclosed box was designed with facility management in mind which allows this box to be 100% weather-proof and windproof. The Grease Box™ Grease Pillows use the same tried and true technology as our Fill-More™ line of Grease Pillows. This means that they ONLY absorb exhaust fan grease discharge, not precipitation, making them extremely effective as well as environmentally friendly. Manufactured from 22-gauge galvanized sheet metal.