The Stealth Kit makes your footsteps silent, and makes your jump kit exhaust nearly invisible.
— In-game description
Stealth Kit is a Tier 1 Pilot Kit that appears in Titanfall.
It decreases the sound made by a player's footsteps, jump jets, impacts, and landings, which makes them harder to be heard by enemy Pilots.
The exhaust produced by the jump kit when jumping is also greatly lowered, making the player more difficult to track. Used with cloak makes the pilot silent and nearly invisible, aside from the grey outline.
The best part about this kit is that you will not make any clambering sounds when you rodeo an enemy Titan. This is useful because the player piloting the Titan won't get any Rodeo warnings or indicators until you either pull off the hatch. If the hatch is already off (either from a previous pilot or you pulling it off prior), then the Titan gets NO notification whatsoever until you begin damaging them.