The Airsoft Headquarters guy explains why his airsoft MK18 rifle equipped with a PolarStar Airsoft Kythera HPA engine is his favourite. PolarStar’s Kythera is a revolutionary HPA system that works entirely without electricity. User don’t need a battery, FCU, or any electronic components to use it. It’s simple to set up and use, resistant to water damage, and has a realistic trigger feel for different firing modes.