A second series of four prototypes was built between 1986 and 1988, incorporating changes resulting from trials with the first two prototypes. These were armed with the Rheinmetall 120 mm smoothbore gun also fitted to the German Leopard 2 and, in a modified version, the US M1A1/M1A2 Abrams MBT. These second prototypes were used for development and then user trials, all of which were completed by 1989, before Japan formally introduced the Type 90 in 1990. Mass production began in 1990, and 30 vehicles were produced by the end of the year.