3-D Glasses
From Sega Retro
The 3-D Glasses was a Sega Master System peripheral which creates the illusion of 3 dimensional graphics in certain video games. The 3-D Glasses use a shutter system to close the left and right lens rapidly to create a 3D effect. The Master System glasses can only be used in the original Master System, since it hooks up directly to the card port not found in the Master System II. Such a system allows 3-D graphics in full color. A disadvantage is that it halves the effective frame-rate, which some users can perceive as flicker. It also tends not to work with non-CRT-based televisions.