HKS  offers Japanese domestic model cars a wide variety of aftermarket parts ranging from engine internals such as connecting rods and camshafts to external parts such as blow off valves, intercooler kits, full exhaust systems, turbo kits, engine management systems and other performance electronics.
The company also produces the  HKS 700E  aircraft engine, under its subsidiary, HKS Aviation. And also produced a 600cc Speedway cycle engine.
Since the late 1980s, HKS has competed in many forms of motorsports including  drag racing JTCC JGTC F3 D1 Grand Prix Superbikes , plus many others. They also sponsor many racers to carry the HKS name and to become part of the HKS team. In the past, they notably used the likes of Anthony Reid (Supertouring/JTCC), Tetsuya Kawasaki (drag racing), Nobuteru Taniguchi (D1 Grand Prix and Time Attack), Akira Iida ( Time Attack ) to drive for their in-house team.