From the same individual who brought us the Everdrive-MD, Super Everdrive and the SMS Master Everdrive. Which are all great products. The price is reasonable at $77 plus 4 S/H. The usually time is approximately 1-3 weeks to get stateside. They are only available from Ukraine atm, until Krikizz ships them to distributors stateside. The only downside is you have to put your own case on it, but that takes nearly no time at all, and makes the price reasonable like I said prior.
Device Description:
Flash cart for Sega Master System/GameGear
+ Max supported ROM size up to 8mbit (1mbyte)
+ 32kb FRAM for game saves keep.
+ GameGear and SMS games are supported
+ Supported standard sega mapper and codemasters mapper
+ USB port for homebrew development*
+ OS can be updated from SD or USB
+ Save ram data can be stored or loaded from SD card
+ Micro SD cards support.
+ FAT16 support. 2GB max partition size
+ Supported Micro SD size 2GB max
+ Flashed game will stay in memory after power off. so no need to choice and reflash game after each reset or power off
cart comes without a shell, but standard shell can be used (without modify)
* USB port available only on "Everdrive GG+USB" cart version
* Homebrew software could communicate with PC via virtual serial port interface. All USB port operations controlled by GG Z80 CPU, so USB port can not be used if cart not attached to console.
Source - http://krikzz.com/everdrive-gg.html









