Plugsuit

The Children in their Plug suits, from the cover of the Carddass Evangelion Special File

A Plug Suit is a form-fitting full body suit, similar to a diver's wet suit, which is worn by Eva pilots in conjunction with their Interface Headsets and aids in synchronization with an Evangelion. No two Plug suits are alike, as each one is custom-made for its owner, and they apparently have multiple spares of each). A Plug suit appears bulky at first, but activating a mechanism on the wrist shrinks it to being skintight. The Evangelion's number designation is stamped on the top of the chest, and onto a triangular apparatus on the back (except for the suit worn by Kaworu Nagisa, which sported an inverted-divided triangle symbol instead).

Plug suits contain various healthy monitoring devices to monitor the pilot's condition, as well as medical aid such as built-in defibrillators. Each of the Plug suits is roughly color-coordinated with their corresponding Eva Unit. Plug suits also have some basic system displays, such as an internal clock able to display how much internal battery power is remaining in the Eva, located on the back of the hand.

Though the basic form of the Plug suit is unisex, there are several gender differences. The male Plug suit has a reinforced area around the chest, with two vent-like structures roughly corresponding to the pectorals. The upper chest and shoulders of the male Plug suits are a different color than the lower parts, and the lower torso has a triangular pattering that mimics the abdominal plating of an Evangelion unit. The female Plug suit is more uniform in color, without chest vents or the plating design, though they have stripes on the hips.

Plug suits do not appear to be absolutely required to pilot an Eva, as there are a few occasions when Shinji piloted without one. Still, it is stated that a Plug suit increases the pilot's synchronization ratio (its not directly stated how, but it seems to "cut down on interference", etc.)