The Middle Aged Gamer likes the APFG MPX K Gas Blowback and it is a GBB that can be easily converted into different lengths to meet airsoft game conditions. It is mainly made of aluminium alloy and fibre polymer, it comes with 30-BB round gas magazine... "It's finally done and what a pleasant ride it was, We take a look at the APFG MPX-K GBB SMG/PDW and I'm very impressed."