The P4B2 controller module has and four potentiometers (knobs) and two push buttons. In your DROID patch you can assign arbitrary functions to the buttons and pots.
The P4B2 is nice if you want more pots than on the P2B8 but don't like the small pots of the P10. And the two additional buttons can for example be used to switch between different layers of pot functions for the four pots.
Shipping includes a short ribbon cable for connecting the controller to the master or to the previous controller. If you want to place the controller further away from the master, you can purchaser longer ribbon cables here in the shop.
The color of the LEDs in the buttons is white.