olive drab cotton twill fabric stretched over the outside. They were discontinued in November 1942 because they degraded quickly in high heat and high humidity environments. They were replaced by evolving plastic liners, using a process developed by the Inland Division of General Motors. These liners were made of strips of cotton cloth bathed in phenolic resin and draped in a star shape over a liner-shaped mold, where they were subjected to pressure to form a liner. The initial "low pressure" process was deemed unacceptable by the Army, but accepted out of need. These liners were made by St. Clair Manufacturing and Hood Rubber Company. Hawley, Hood, and St. Clair's contracts were cancelled by early 1944, when a "high pressure" process which produced better-quality liners became commercially viable. Companies which produced "high pressure" liners during World War II included Westinghouse Electric & Manufacturing Company, Firestone Tire and Rubber Company, CAPAC Manufacturing, Inland (whose molds were acquired by Firestone after their contract was cancelled), Mine Safety Appliances Company, Seaman Paper Company, and International Molded Plastics, Inc. Liners essentially identical in construction to "high pressure" World War II examples were produced between 1951 and 1954 during the Korean War by the Micarta Division of Westinghouse and CAPAC Manufacturing. In the 1960s, the M1 helmet liner was redesigned, eliminating the leather chinstrap, nape strap, and changing the suspension webbing to a pattern resembling an asterisk in a coarse cotton web material in lieu of the earlier cotton herringbone twill. In the early 1970s, suspension materials changed to a thicker, more flexible nylon with a rougher unbeveled rim. Later changes included a move to a yellow and green material for liner construction. Paratrooper liners M1 helmet liners intended for use by paratroopers had a different construction. The short piece of webbing which held the nape strap at the back of the wearer's neck was extended around the sides of the liner, and terminated on each side in "A" shaped yokes which hung down below the rim of the liner and had buckles for an adjustable chin cup made of molded leather. Two female snaps on the inside of the liner above the "A" yokes accepted male snaps on each of the steel shell's chinstraps, and helped to keep the liner inside the steel shell during abrupt or violent movements. Accessories Cover In late 1942, the United States Marine Corps used a cloth helmet cover