It's the double deluxe side mount.
The long 1.5 x 3 profile is extended from 21 inches to 23 inches.
The 1.5 x 1.5 support upright profile has been extended from 14 to 16 inches.
2 more cross profiles have been added to mount a second shifter/handbrake/flight gear.
the entire side mount has been reinforced with an additional 2 brackets to handle your extra gear.
Includes:
everything in the Phantom Deluxe Side Mount and:
2 extra cross profiles 9 inches
6 extra corner brackets.