The FI SYST 165 is a 2-way speaker system with a 6.5"/165 mm carbon woofer equipped with a large voice coil, and a 1"/25 mm tweeter with neodymium magnet:
The tweeter uses the ESB CS-FIT1 1"/25 mm component tweeter, with special adaptor to fit many Fiat/Iveco vehicles, as well as some Citroën, Opel, and Nissan models..
The woofer uses the ESB CS-FIW6 6.5"/165 mm component woofer, with special adaptor to fit many Fiat/Iveco vehicles, as well as some Citroën, Opel, and Nissan models..
Crossover: ESB CS-FIT1CX dedicated crossover. 
Compatibility: See Data Sheet