ZCI V2 M4 Upgraded Gearbox

ZCI V2 M4 Upgraded Gearbox An upgraded Version 2 gearbox by ZCI fitted with an M4 trigger and selector plate. This is built with 8mm bushings, a quick-detach spring system, a standard trigger and trigger board. Features: Metal gearbox shell Quick change spring 8mm bushings Standard trigger unit Standard trigger Full bore cylinder