Those muffles are made with a excellent “super” down (Fill Power 700 cuin). A windstopper fabric is used for the external face.
The adapted shape allows to retain all the functions of the usual brake control (which remains in the sleeve in flight). On the floor, you can mount the sleeves easily, with a suitable tightening, in the upper part. Your usual handle will stick to its classic location, by its classic pressure, or magnetic.
The sleeve allows the passage of your brake handle in the upper part, for easy control, hands warm. Inflate your wing in a thin glove or bare hand then quickly put your hand in the sleeve, taking your handle as usual.
Fly for hours, and keep your hands hot !
The low opening of the sleeves, by its shape, allows easy access to the brakes. Inside, a breathable face (Goretex style membrane), hides a pocket covering the hand palm. In this internal pocket, you can add a chemical heater if really the very cold.