The SplitFire Super Direct Ignition System is designed exclusively for the Japanese high performance engines. This system replaces the original equipment coil pack and ignition wires with a direct ignition coil on plug system. The increased ignition performance found with the SplitFire Super Direct Ignition System is a must for all racing and performance enthusiasts. FEATURES:- > Increases horsepower at the top end of the RPM band > Ensures and maintains maximum energy supplied to the spark plugs > Reduces incomplete combustion caused by misfire > Eliminates RFI (radio frequency interference) by eliminating the need for a wire set > Easy installation designed to fit the high performance engines NOTE: > The difference between the Nissan Skyline R33 GTS-t RB25DET series 1 and series 2 are the igniters. The series 1 have separate igniters, where the series 2 are built in. You should be able to tell by looking at the existing coil packs. Alternatively you could look up the engine number with Nissan if not sure. > RB20DET harness may be required for older vehicles *Please ensure the product number matches your car model.