The APS CAM870 shotguns were already probably the most realistic and innovative shotguns on the market, but APS went and made them even better by releasing the CAM870 MKII. The mark 2, or MKII, has simplified the awesome shell ejecting design, making it a little bit cheaper and waaay easier to use. But just as realistic and as fun! Previously you had to use a very fiddly device to hold the shells like a vice to charge them with CO2, but that's all gone. On the MKII the CO2 is charged directly into the bolt using the supplied nozzle and a 88g CO2 cylinder (available separately). Together they act just like a bottle of Pro Gas when filling up a regular GBB mag. The MKII shells have holes that allow the CO2 to travel through, blasting out your prepared chosen ammo, wadding and sealing paper, just like the real thing. The shells are cheaper than before too. So it's more affordable, easier to use but just as realistic and as epic as before, win win!