The Assault kit is made for players on the frontlines. Armed with Assault Rifles, players enemies from a variety of ranges as they gain ground for their team. In Battlefield 3, the Assault kit is also given the Gadgets from the Medic kit in Bad Company 2, and the are able to heal and revive their teammates on the fly.
The Engineer kit arms players with a variety of Anti-Vehicle weapons. Players are responsible for the destruction of enemy vehicles as well the repair of friendly vehicles, and are able to disarm enemy C4 without an explosion. Engineers have the ability to equip a flashlight on their Carbines, which enables them to light low light areas as well as blind enemies at close range.
The Support kit has a selection of Light Machine Guns at their disposal. They have the ability to suppress enemy infantry, which blurs their sight and stops health regeneration.
With the introduction of the ability to go prone, Sniper Rifles are no longer an one hit kill to the chest, and glare from their rifle scope gives away their position.