The most uncomfortable mask. Face too big for a grown man (tall man 6ft 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 digs into your cheekbones if that's not enough. Complete garbage mask and company.