Although these boots are warm, they are not as warm as One Sport boots. Super Gaiters, which are gaiters filled with holofil or some other synthetic material can be used over the double plastic boots. Inside the boots climbers wear a thin or mid-weight liner sock made of polypropylene. A wool sock is used on top. Wool stays relatively warm even if it gets wet from sweating.
Some climbers use electric socks.
Electric socks are found at fishing stores and run on batteries. A small electric element under the ball of the foot helps keep feet warm. Despite all these measures some people still get frostbite on their toes.