The Boss GA-FC EX Foot Controller represents the logical evolution of the previous GA-FC Controller and comes with some useful new features on board. Designed for a wide range of typical Boss amp models, the foot controller now features dual-colour LEDs for accurate monitoring of switching status and comes with two connectors for expression pedals for real-time control of individual effect parameters. furthermore, there is an additional connector that can be used for either a third expression pedal, another GA-FC or GA-FC EX, or as an output jack for controlling a second amp.
The Boss GA-FC EX Foot Controller at a glance:
Foot controller for Boss amplifiers
Five-foot switches and function switch
Two connections for expression pedals
Two-colour LEDs for switch status indication
Control connector with three switchable operating modes (Expression 3/Expand/Foot Control 2)
Robust metal housing
6.3 mm TRS jack cable included
Compatible amplifiers:
Katana-100, Katana 100/212, Katana-Head and Katana-Artist.
Nextone Special, Nextone Artist and Nextone Stage
Waza Tube Amp Expander
Katana-210 Bass and Katana-110 Bass
Acoustic Singer Pro and Acoustic Singer Live
Roland Blues Cube Artist, Blues Cube Artist 212 and Blues Cube Tour
Line 6 FBV3
Marshall PEDL-91016 6-Way Latching Footswitch (Origin Series)
Boss GA-FC Controller Footswitch 
Boss FS-6 Dual Footswitch