Yep, airsoft parts is an amazing retailer and my first choice always. Just wish they would stock MP5 handguards..
Anyways those King Arms Magazines will impress you. If you got the plastic ones, it's a shame they even call them plastic. They are extremely sturdy and when i had my spr i had the VN Mags. With a slight slight cut to the mag retention lip, they fed flawlessly 100% of the time. They really are the best midcaps out there.