The Hollis M1 Mask is on the pricier side, but its revolutionary structure and high-quality supplies make it a worthwhile financial investment for critical divers. The Hollis M1 is usually a frameless diving mask with a 100% pure silicone skirt. It's a minimal profile and will fold flat for packing. https://dantepzfou.thezenweb.com/the-smart-trick-of-high-quality-silicone-masks-that-no-one-is-discussing-66232302