 Numerous aftermarket modifications and upgrades are available for 200 and 300 Series King Airs.One company offers a Wing Front Spar Reinforcement Kit for 200 Series aircraft and a modification to replace the electro-mechanical landing gear retraction system of early-build aircraft with an electro-hydraulic system.Raisbeck Engineering out of Seattle, WA offers Enhanced Performance Leading Edges, Nacelle Wing Lockers, Ram Air Recovery System, Quiet Turbofan Propellers, High Flotation Gear Doors and Dual Aft Body Strakes.