We felt the protector should be a silent partner in crime: so light and breathable you forget you have it — until an emergency makes you thankful you do In a practical sense, it needed to protect against almost anything and fit snugly on your mattress, without compromising breathability. The Casper mattress protector won’t change the comfort of your mattress or affect the temperature. After several rounds of thermal and humidity testing, we settled on the optimal film for spill protection and breathability. It happens to be the same kind used in state-of-the-art outdoor gear. The protector's unique skirting offers a superior balance of stretch and recovery to fit your mattress like a glove — accommodating mattresses that are up to 16 inches thick. This 360-degree grip prevents shifting, and the cross-directional stretch and machine directional elastic allows the fabric to move with your mattress instead of popping off. We included Casper labels to indicate the head and foot of the bed and make life easier.