The Vamo mod has the electronics housed in a metal tube that is solid on one end with a hole drilled in it for the center connector. this means that the + contact is surrounded by metal, with a small gap between it and the metal. A nipple top battery must be used with this Mod in order to clear the metal surrounding the + contact. A flat or button top battery can short out due to this design. I had this happen to me and I got lucky, all it did was melt the hot spring. Be very careful with this Mod and use only Nipple top batteries to prevent shorts. I thought that China was starting to listen to what we want as this Mod is VV and VW along with Avg or RMS output. It works great, but should have come with a warning about the batteries. It does no good to have the latest technology in a device if it blows up in your hand. Come on China, spend a half a ...kin penny and put a plastic sheet in top of this Mod and fix the damn thing before somebody gets hurt!!!