3-D Adapters for the Sega Master System are known for getting flakey with age. Sometimes one eye will go dark or sometimes they won't work at all.
If you need a replacement for your 3-D Glasses Adapter - our's aren't merely "tested". We open each adapter, thoroughly pre-clean the circuit board, and run each one through our heated ultrasonic cleaning process. The 1/8" glasses jack is resoldered, capacitors replaced, and each unit is given a final test.
These 3-D Adapters can also be used with 3rd party LCD-shutter type glasses - original Sega glasses not required! While the original Sega glasses are a nice collectable, they were fragile and prone to breaking even when new.