The Hotronic S4 Universal and Hotronic S4 Custom foot warmers are almost identical products. The main difference is that the Universal model comes with heat ready, universal insoles that can replace, or be interchanged with, your current insoles.
If you have replaced your factory ski boot insoles with custom or orthopedic footbeds, then you may prefer to opt for the Custom model and simply install the heating elements into your current insoles. The custom kit does not come with heat-ready insoles.
Both kits include two battery packs, a charger, two heating elements, and a pair of adhesive strips and covers. Hotronic S4 foot warmers utilize two battery packs that are powered by AA NiMH cells. There are three different base settings, as well as an “extra blast” setting that can be initiated intermittently at 3-minute intervals. These batteries operate well in cold conditions and last up to 21 hours on the lowest setting.
The heating elements are compact, oval disks that fit comfortably in the universal insoles. Once installed, you can apply the adhesive Cambrelle covers on top of the insoles and heating elements. This lining is moisture wicking and evenly distributes the heat across your foot.
The packs come with a clip that can be attached to the power strap of your ski boot. Many customers have reviewed that this clip isn’t strong enough, and therefore they have lost the battery while skiing or riding. We recommend purchasing the additional slide strap bracket because it helps to secure them better.
