It is a metal Cyma M4, P&J used to use A&K's but they are using the metal Cyma's now It looks like it has a metal hop and maybe a working bolt catch too but don't quote me....     400mm barrel is a bit long for my liking but I'm being picky now for that silly price metal flip sights, not plastic snap off type on £70 plastic Cyma's couldn't give a toss about ambi mag release though not a grean fan of stock either but I'm being fussy, not sure about