It is about 4" across. Fits perfectly where the reflector was.

Wires are about 10-12" long. Plenty enough.

I had already cut into my harness so it wasn't anything, but you need your brake power and a ground...I soldered them in on the bike side tail light plug. There is a yellow wire that you use to select your flash pattern. Power up the light then touch yellow to 12v and it changes to a different pattern. Easy enough