The M50 joint service general purpose mask is the United States armed forces' field protective mask, which began service in December 2009, replacing the M40 field protective mask and MCU-2/P.
M50 joint service general purpose mask Wikipedia
The M50 is certified to MIL-SPEC PRF-EA-10003. The M50 is compact, light, comfortable and more effective as determined by the Defense Department Joint Program Executive Office for Chemical and Biological Defense. The M50 allows for a wide field of view with a single lens that spans the width of the face. The M50 has twin conformal filters, which decreases breathing resistance by 50 percent. This protective mask provides 24 hours of continuous eye-respiratory protection in nuclear, biological and chemical (NBC) environments. Another feature is an indicator which turns blue when the filter has expired.