3D Active Shutter Eyewear:Highly precise control completely closes the shutters for both eyes at the instant that the images change for the left and right eyes. This masks unwanted afterimages to enable clear and comfortable 3D viewing.World"s lightest:Approx .085 lbsSize small 3D EyewearHeadsize 18.8-20.8" Around Rechargeable Battery for Repeated UseBuilt-in battery is charged using a USB terminal Easy to-operate slide switchPower On/Off Switch. The slide switch makes it easy to turn the power on and off. 3D Active Shutter EyewearHigh-Precision Shutter Control Sends Clear Images to Each EyeHighly precise control completely closes the shutters for both eyes at the instant that the images change for the left and right eyes. This masks unwanted afterimages to enable clear and comfortable 3D viewing.Fits small head sizesThe eyewear fits head size 18.8-20.8" AroundPower On/Off SwitchThe slide switch makes it easy to turn the power on and off.Designed for Use Together with Ordinary GlassesThe 3D Eyewear can also be comfortably worn right over ordinary prescription glasses.Lens Case Included