Master Gear Converter

Picture from Sega Retro

The Master Gear Converter is a third-party add-on for the Game Gear that allows you to play Master System games. It was also known as the Master Gear, Gear Master Converter and Master Gear Adaptor. Some variants were officially branded Sega items.

It is a simple passthrough adaptor from the Master System cartridge to the Game Gear cartridge slot. It additionally connects a pin in the Game Gear slot to enable its built in Master System compatibility mode.

Some Master System features are unavailable, such as card support (although a Card Catcher could remedy that), 3D glasses support, and Light Phaser support.