45North's Jaztronaut are temperature-blocking insoles designed for cycling footwear. These insoles are constructed with a 2mm panel of non-compressible aerogel insulation laminated inside durable EVA foam. Aerogel is a porous nanotechnology that has been used by NASA to insulate astronaut spacesuits! It has super-high thermal performance and does not require loft to trap heat. Simply put, these insoles say no to cold cleats, and yes to warm feet, even under pedal load.