This was an AK professionally build by Polarstar. The engine inside is a mechanical Kythera engine with being professionally put together by polarstar, there is not trigger issues. It uses 33g Co2 cartridge that lasts around 400-500 shots per cartridge. The serial number on the engine is “DEMO-003” so it’s one of the first engines made. Hop up is also upgraded as well as the barrel, to a high ore barrel. It comes as you see, price is BEST OFFER. NO TRADES. SHIPPING AND HANDLING ON THE BUYER. I can meet up in FL or CT. Any questions feel free to ask.