Lot of two, WWII US Army M4 Lightweight Gas Mask with covers. Both masks are in excellent condition still retaining the original filters. Excellent The M4 Lightweight Service Mask was a gas mask used by the United States during World War II. The unsatisfactory weight and bulk of the M2 series masks led to the development of an improved service gas mask. In 1942, the M3 Lightweight Service Gas Mask was standardized, weighing only 3.5 pounds vs. about 5 pounds for the M2. It used the molded rubber facepiece from the M2A2 mask with the addition of an interior anti-fogging nosecup, and an improved, lighter M10A1 filter canister. The changes and improvements retained the same level of protection to the wearer as the M2 series mask. The corrugated hose between the facepiece and the canister was shortened to save materials. The M3 was manufactured from both grey rubber and black Neoprene (synthetic rubber). The Neoprene was found to become unusable in cold weather due to hardening of the mask under those conditions while the natural rubber remained flexible even in cold weather. In 1944, the M3A1 mask was released featuring an improved outlet valve. Over 13 million of the M3 series masks were produced during World War II. The M3 series remained in use until obsoleted in 1949. M4 Lightweight Service Gas Mask In 1942, the M4 Lightweight Mask was standardized to add additional improvements. It had many features in common with the M3 series, including the M2A2 facepiece, internal nosecup, outlet valve, shorter hose and lighter M10A1 canister. The M4 series masks were made of natural rubber in olive drab color. The Army ordered 250,000 of the masks. A modification to the outlet valve resulted in the M4A1 Lightweight Mask in 1945. The mask was obsoleted in 1949.