Easy Equalization The IST Pro Ear Series features four incredible designs, each offering pressure equalization technology through a tube and seal system that's unique to IST. Simply exhale into the mask and your ears immediately clear. The watertight cups not only help with regulating pressure, they also keep your ears warm and help prevent ear aches and infection. Incredible Performance The dual-lens design provides a crystal clear view while the tempered glass material maintains solid durability. Adjustable straps help you get the perfect fit and a clean seal so there's no leakage. Comfortable Fit The Pro Ear masks are characterized by wide head straps that distribute pressure to a larger surface area to eliminate squeezing, pinching or painful discomfort. Plus, an extra fabric fastener strap extends over the top of the head for a secure fit.