This is a custom made Iron Man 2 and Avengers style Arc reactor. The housing is made from CNC laser cut steel then welded and ground smooth. A chrome powder coat is applied, this finish will not scratch and is very durable. The outside diameter is 3.5" and about 3/4" thick. The custom PCB is based on a Arduino and has 30 super-bright LED's all with fading and has different animations that you cycle through by pressing on the center. Each unit includes a battery pack as well as 2 elastic straps with hooks to wear the arc reactor. This is a great prop for you use for your next cosplay or a very unique display item. Check out the following video for some examples of the sequences. you can check out a video at: http://www.youtube.com/watch?v=4LKtO71osd0&list=UUxHfm1RpHaDNLGidgM1PIIA&index=1&feature=plcp