Free sales tip: Packaged snorkeling sets are a good way to get started. All of the sets we sell are high quality. Masks in the set are made of tempered glass and silicone skirts. Be aware of inferior masks made with PVC. PVC is not soft and resilient like silicone. What does that mean? PVC is stiffer and not as conforming as silicone, the better a skirt the less chances of leakage.