You can have up to 3 Perk slots, they don't have a level requirement, the first one is free and unlocked from the start. You will permanently unlock the two others for $10000 and $100000 respectively.
They can be bought and changed using the "Change Perk" menu at spawn. You can check what perk you have currently equipped at all times, they are displayed on the bottom right side of your screen.
Increases money rewards by 10% and reduces price when buying your last loadout by 50%
Gives you twice the ammo for your primary and secondary weapon. See Weapons Attachments
Allows you to repair any friendly or empty vehicle on the battlefield to a working condition.
Engineer also gives you a compact variant of 7 ARs.
TRG-20, MK20C, Katiba Carbine, MXC, ADR-97C, AKU-12, Promet 6.5mm
You receive five medkits instead of two and revive downed teammates twice as fast. Reviving and healing gives you bonus money and experience. You also get 2 extra smoke grenades
Grants access to Anti-Tank, Anti-Air and Anti-Personnel launchers.
Grants access to sniper rifles, DMRs, long range scopes and ghillie suits. Your binoculars are replaced by a rangefinder.
Grants access to machineguns.
It will also give larger magazines on all weapons, if available
Adds an underbarrel grenade launcher on compatible weapons and increases the amount of hand thrown explosive and smoke grenades carried.
If combined with the EXPL perk you get additional underbarrel grenades.
Quicker stamina regeneration.
Automatically deploy countermeasures in a vehicle if being fired upon by a lock-on missile. In ground vehicles you have to be in the commander seat.
Replaces your binoculars by a laser designator with built-in thermal and night vision.
Adds a silencer to both your primary and secondary weapon if compatible.
Gives you access to a satchel charge, increases the amount of explosives you carry charge plus additional rockets for your launcher. See Launchers
Adds a bipod to your primary weapon if compatible.