Information from Bung website (now defunct)

Case:
The physical size of the Doctor GB card is near identical to an original Game Boy cartridge.
There are four colors currently available for GB Card (4M) and they are red, grey, yellow and green.

ASIC:
The newly released version 2 of Doctor GB card has a built-in custom made asic fully developed by Bung Enterprises Limited.
The power consumption is less than 9% compared to version 1. A Gameboy Color with a fresh sets of alkaline batteries can
last about 20 hours with our new version GB Card.

FlashROM:
There are currently three models of the GB card, each has 4M (4mbits), 16M (16mbits) and 64M (64mbits) FlashROM
built-in respectively. Data can be retained inside over five years and number of upload and download is nearly unlimited.
FlashROM does not need any power supply to retain data. The performance of the burn in time for our GB Card is unmatched
by any other competitors.

SRAM:
GB Card (4M) has built-in 256 kbits SRAM,All model supports Game Boy MBC1, MBC2 and MBC5 format ROM & SRAM.
With multiple game pack into one GB Card, built in SRAM is able to store up to 15 different games automatically for 4M GB Card.