The GHP12 brings Garmin's full featured, marine autopilot technology to 20- 70ft sailboats, as well as powerboats with solenoid steering systems, cable actuated steering systems and 3rd party hydraulic pumps. When interfaced with Garmin's GWS10 or compatible wind sensor, GPS and network electronics (all sold separately), the GHP12 can support heading hold, wind hold, step turns, tack/jibe and much more. For sailboat applications, there are two linear drives available from Garmin, capable of driving many different steering systems and that fits almost any midsize to large sailboat (depending on the particular installation). Sold separately. Class A drive unit is for sailboats with up to 28,500lb displacement. Class B drive unit is for larger sailboats with up to 79,000lb displacement. If you wish to connect a GHP12 to an existing steering system (cable or hydraulic) the boat must be capable of providing rudder position feedback to the electronics control unit. GHP12 Kit includes the following: GHC helm control unit GHP12 Electronics Control Unit (ECU) GHP12 Course Computer Unit (CCU) CCU/ECU interconnect cable (with threaded collar) Buzzer GHC cable 2 NMEA 2000« drop cable (2m) ECU power cable (with threaded collar) NMEA 2000 power cable 3 NMEA 2000 T connectors 1 male and 1 female terminator Documentation.