MK4-Key is almost same with MK4-mini,only have one different: MK4-Key don't have the EEPROM chip to keep the nds saves
The MK4-Key finally SPEC:
Mini - Just same with the original NDS cart size.
Support ALL NDS & Lite --- Support any version of NDS & NDS LITE.
Brightness adjust --- Can adjust the brightness level of NDS / NDS lite, keep all nds function with you.
Auto Sleep Mode --- 100% hardware support NDS power sleeping mode,you can close the nds case and open it in anytime, the game will keep to running, just same as one original NDS cart.
PLUG and PLAY --- 100% don't need modify your console,just need to plug in the MK4-mini,then can make all version of nds/nds-lite works immediately.
GBA/NDS Swap --- You can boot any flash cart (like the NEOFlash / XG / SC / M3 / EZ / MP / GBALink) form GBA slot,and you can boot MK2 / MK3 serial form NDS slot too.
R-S-A Secure --- 100% support R-S-A secure arithmetic.