got the brines for my girlfriend Fußkalte bought, which is very happy now. The price is borderline, but all other solutions (with cable to the shaft and battery pack outside of the shoe) I regard as impractical. At the lowest level is about 6.5 hours after closing (at temperatures around 0 to + 7 degrees). Eight hours and more are possible in midsummer accessible .... Have the sols every now and then unloaded / loaded in the summer and am curious how long (permanently installed) battery lasts.