Most LEGO keychain lights are made from ABS (Acrylonitrile Butadiene Styrene); at least one option is listed as a rubber construction.
The LEDs are placed either in the feet or the bottom of the figure, and the light is turned on and off with a switch located in the chest.
Listings show heights of roughly 2 to 3.75 inches. Many models are described as about 175% the height of a standard LEGO minifigure, while one listing describes a model at about 300% of a specific minifigure.
They commonly include a metal key ring for attaching to backpacks, purses, lanyards, or keys.
Listings indicate batteries are included, and at least one review notes the batteries are user-accessible and replaceable.
Descriptions say the lights are useful in dimly lit areas; a review characterizes the brightness as moderate—suitable for reading in low light but not very strong for long-range illumination.