I've made these little LED lights for years for people looking for easy ways to add lighting to everything from cosplay to doll houses to holiday decorations. These lights are color changing RGB (red, green, and blue) 5mm LEDs connected to a small battery pack. Each order contains 4 complete lights with 2 batteries installed and 10 extra CR2032 batteries. You can operate lights with a single battery too. The battery pack measures approximately 2 1/4" x 1 1/4" x 1/4" and has an on / off switch. Wires usually extend about 5 1/2 to 6". Each small LED bulb contains 3 tiny diodes in red, green, and blue, with each slowly fading on and off. These are the primary colors for light, so as the colors combine, you will see many additional colors. Battery brands may vary, but I always use fresh, carded batteries. Please note, CR2032 batteries may pose a choking hazard, so keep them away from small children.