TThe original MKII Kit has been discontinued as of December 1, 2016. The MK2.5 Kit is the replacement for this product and can be found here: Compatibility information between the two products can be found here: The Protech Airsoft MKII is a drop in HPA system that will fit into almost any v2 standard gearbox. This unit allows you to use existing gearbox shells so that you can maintain the original functionality of bolt stops, and ambi controls of your existing AEG. Key Specs: -40 to 120psi Operating pressure range -250fps to 550fps w/.20g BB -Aluminum nozzle -Standard non-BlueTooth FCU with LCD and joystick menu navigation -T6-6061 Aluminum construction -Extremely low current draw FCU (4+ month battery life in standby) -Custom nozzles are available by contacting us : email@example.com Included with the V2 Kit: -V2 trigger board -Wire harness - 14" length -MkII V2 HPA Engine -Standard FCU -Buffer Screw Retention nut(replaces spring guide on guns that require a spring guide to hold buffer tube in place) Instruction Manual and Registration for your MKII can be found at the following link: Click here By Registering your MKII, you will be eligible for your warranty and Bluetooth FCU voucher upgrade. This voucher ties with your serial number and will be eligible to all MKIIs purchased before the release of the Bluetooth FCU.