Implant
Implants are upgrades that you apply to your character that improve your performance in combat in various ways. There are three different implants at each rank and you can only choose one, but if you change your mind you can change the implant for a fee of 50,000 credits per implant, or 500,000 credits for full reimplantation. You can only equip implants up to the highest rank of ship you own.
Implants only take effect when flying a ship of the same rank or higher, so a rank 3 implant will work on a rank 3 ship or higher, but will not work on a rank 1 or 2 ship. The sole exception are the rank 15 implants, that give a bonus to synergy and/or credit gain that applies at all times.