Lens material: 4mm thick tempered glassMask material: PVCHeadband: TPR materialSteel ring: stainless steel frameTempered-Glass Lens for Safety: Forget flimsy plastic lenses This one is quality tempered glass, which resists scratching and shattering.Convenient Buckle for Easy Adjustment: Simply pull the straps to desired fit and the buckle will hold the straps securely in place. Presto: customized comfort.Rugged Enough for Scuba Diving: Thanks to its sturdy construction, your mask can stand up to all kinds of wear - from snorkeling in the pool to deep-sea scuba diving.One-Piece Lens: A snorkel mask should help you see better, not obstruct part of your view. Now you can enjoy all the underwater scenery clearly.