The number of special 3D eyeglasses included with the 3D TV. Some 3D TVs omit this item to control costs. Some 3D Blu-ray players may include these glasses. Retailers may offer a "3D TV + Blu-ray" bundle that also includes the glasses. All of the 3DTVs in our Ratings require the viewer to don special eyeglasses. So-called "active" 3D sets, which require "active" battery-powered LCD shutter glasses, may come with one or more pairs, or none. Additional pairs generally cost from $50 to $150 each. Most so-called "passive" 3D TVs come with four pairs of passive polarized glasses, much like the ones used in theaters, which don't require batteries. Additional sets cost from $10 to $30 each. You cannot use passive glasses with 3DTV that requires active glasses, and vice-versa. You also generally cannot mix active 3D glasses from one brand of TV with another's, though TVs made in 2012 and later may share glasses. (Passive 3D glasses can be used interchangeably with any passive 3D TVs.) There are some "universal" active 3D glasses you can buy as an after-market item .