Product Link:
http://www.nkcelectronics.com/MEGAshield-KIT-for-Arduino-MEGA-2560-R3_p_309.htmlProduct Image:

How to use it with the Arduino DUE board, in 3.3V:

Set the power jumper to 3.3V to bring 3.3V to the central positive power bus. All I/O ports on the DUE are 3.3V and NOT 5V tolerant. You can damage the DUE board by sending 5V signals to any of the DUE I/O ports.
Another difference is that the DUE has Analog Input 0 to 11. Pin 12 is DAC2, Pin 13 is DAC1, Pin 14 is CANRX and Pin 15 is CANTX. This is only a silkscreen (text on the PCB) difference. Each pin from the MEGAshield goes to the corresponding pin on the DUE board.