Big Brother Vari-Cool is now available. This has a new switching regulator, which improves the battery life even more over the V1. It adjusts between 1 volt and around 6.5 volts, and produces almost no heat.  The regulator also limits the amount of current going to the switch, protecting it. There is no master on/off switch. Dial it down when putting in purse or pocket. This mod uses 2 14500 3.7v LI protected or high drain batteries, not included. A dual charger, and high drain batteries are recommended. Size is approximately 1.27X2.6X.6.There is a 7 day wait on the Big Brother mod.