What material is embedded in the rubber footing?
What is the "rubber foot" made of? In converting my Amazon Echo to mobile use with UPS, I tried to drill the metal(?) plate within the rubber foot but nothing would attack it, neither tungsten nor carbide. Since there are no wires, I am hoping this is not a critical part because I had to eliminate it during modification reassembly. Everything seems to work fine and the small UPS installed in a small attached base box runs for approx 1.5 hours.