With all the same features as the Single Pane Lenses, the Proto Switch Thermal Lens includes a dual layer to help reduce fogging. Lens fog is caused by air inside your mask being hotter than the air outside your mask. By adding a second layer, we create a buffer so the temperature around your lens is more even, there by reducing fogging and allowing you to play with clearer vision. Proto thermal lenses also include an anti-fog coating to help further reduce fogging.