Cold feet and thick overshoes are always a bugbear, but this winter we've almost done away with overshoes thanks to these heated Grisu insoles. After initial splutters at the price, we wouldn't swap them for anything.
Operated via remote control, the thermal insoles house a lithium-ion battery at the rear with the heating element lining the front footbed.
Compared to regular insoles there's a slight increase in height and they are heavier, but they're anatomically cut, comfy and very supportive. The Grisus were actually designed for Alpine ice climbers and skiers so they easily handle the pressure of rigorous riding.
Once turned on, a microprocessor regulates temperature at 38ºC – you really notice the difference and toasty toes when things get really cold outside. The heating element also shuts down should they get immersed in water to prevent any damage to the electronics.
The big advantage of the Grisus is that you can ditch the bulk and awkwardness of an overshoe. Even in the really cold weather we got away with backing them up just with neoprene toe covers.
Heating lasts from 4-6 hours and they take four hours to charge to full. That charge will drop off if you don't use them, but lithium-ion batteries don't have the memory effects associated with some battery types. They do however have a finite shefl life, which means they are best stored in the fruidge if you are going to stop using them for a while.
In fact the only problem we had was misplacing the remote or forgetting to turn them off. The run time lasts easily enough for a long ride, especially once they've warmed up.
You can use them in any shoe with a removable insole.