I and my son are Gundam fans. A while ago, my son bought a Bandai MG Gundam 00 Seven Sword model kit and noticed it can take GunPla LED for the head, GN Drive and sword. We are excited that it's quite easy to get the kit light up but soon we found that it's not convenience to turn it on/off. And it's troublesome to change batteries and they doesn't last long. Also some units had bad contact on the battery holder causing the unit dim or flicker. All these make me try to make a LED unit that's easy to install/change batteries, easy to turn it on/off without poping it out all the time and it have to use a larger battery so that it last longer. After some prototype and testing I finally settle on this design that it have these advantage: