The K-1 full pressure helmet was designed and developed at the US Wright Aero Medical Laboratory and was to be worn with partial pressure suits.
The helmet consisted of a rubber bladder that completely covered the head, sealed using an inverted flap at the neck.
A snug, laced-nylon restrainer and a close fitting, green fiberglass outer shell limited the ballooning of the bladder (The first K-1 version had a two-pieces split hard shell fitted over the hood by means of a curved metal fairing).
Earphones and microphone were supported by foam rubber padding inside the bladder, and a removable electrically defogged plastic visor ( made by two flat pieces of tempered glass held in place by a hard rubber frame in the early version) contained the necessary inhale/ exhale valves. The shell was fitted to both inner, lower rim with brackets where the deflection pulleys of the anti-elongation cable harness were secured.
The helmet design had also some shortcomings: at high altitudes with great sky-cockpit light intensity variation, the visor could impair vision, making it difficult to read instruments. Another problem was the severely hampered wearer’s head mobility, thus significantly reducing his field of vision. Some of these problems were solved with the MA-2 implementation.