Product details:
The Hotronic S4 Series Footwarmers Power Plus Set offers you enhanced reliability, longevity, and performance over the older M Series and E Series batteries. The S4 Series batteries maintain up to 55% of a full charge and 95% of their initial capacity after four years of non-use! Plus, an increase in capacity offers up to a combined 30% in higher average temperatures and longer durations on a single full charge, when needed most, in the cold! The S4 Series has a 4 cell battery.