These tiny (3cm tall by 2cm wide) electronic pendants are very detailed and richly detailed with printing on the PCB of the (BttF 3) car in profile, and a miniature form of the "flux capacitor warning" symbol on the front. The rear says "1.21 gigawatts" and there's a good-sized through-hole for a chain or necklace. The LEDs are extremely bright and super tiny. The start button causes the pulsing light pattern to increase in speed for a short time and then it resumes its slow pulse. One rechargeable LIR2032 battery lasted about 18-20 hours with continuous use. There is no documentation; It doesn't need any. The item comes in a static baggie. I didn't communicate with the seller but the product arrived very quickly. Beyond that, I bought two just in case the toy car I installed it in traveled to a distant time and became lost. This hasn't happened so far, but I'm still treating it with caution.