They showed up a few months ago, they've been relocated to different poles occasionally but I've never seen it being done. I didn't get an exact measurement but if I had to guess I'd say around 4in x 3in x 1.5in. Not sure of the material but kinda looks like plastic? I don't see any cables coming out of it so I assume it's battery-powered. On the top is a hole that looks a bit like a lens and on the bottom is some kind of vent