The Stadium GTO 20M is intended for use with the Stadium GTO two-way systems, or to replace existing midrange speakers in systems that are already three-way from the start. The Stadium GTO two-way component systems are 3-way upgradeable. The crossovers are gap-switchable to accommodate a midrange upgrade. The optional Stadium GTO 20M midrange includes a bandpass crossover to convert a two-way system into a threeway system with perfect tonal balance. You simply connect both crossovers to the speaker wires from your car amplifier in parallel, and set the existing GTO two-way crossover to GAP function. Stadium GTO 20M is designed to also fit into many factory three-way applications. Please note that you cannot use this add-on midrange with coaxial car speakers, unless you can access the crossover networks to establish the midrange gap that the extra midrange is meant to occupy.