The world's most uncomfortable mask Too big for a grown man's face (1.80m tall). Extremely poor design and poor fit lead to very serious leakage problems. The rating doesn't matter if you have a leak, period. There can also be an efficiency of 0%. Good luck trying to wear this for even 20 minutes let alone 8 hours. It even bites your cheekbones if that wasn't bad enough. Complete garbage mask and company.