These light-up track cars are so cool - kids go absolutely crazy for them. This is a 3-pack replacement set (red, blue, and yellow) that works with most track systems as long as the inner width is at least 2.2 inches. Each car has 5 LED lights that flash and make them glow in the dark, which looks amazing when the room lights are dim. They're made from safe ABS plastic and are super simple to operate - just flip the switch on the bottom and they're ready to race. They need 2 AA batteries each (not included), but we'd recommend getting rechargeable ones since kids will want to play with these constantly. The cars measure about 3.8x2x3.1 inches and work on any smooth surface, not just tracks. They're great for encouraging social play since three kids can race together. The plastic is a bit thin to allow the light effects, so try to avoid hard crashes against walls. Comes with a small screwdriver for battery changes. Perfect birthday or Christmas gift that won't break the bank.