Single pane lenses are made of a single pane of polycarbonate material that gets the job done when it comes to keeping your eyes safe from paintballs. They often have an anti-fog coating but don’t eliminate it completely.
Dual-pane lenses have two panes molded together than ensures good maintenance of temperature. This means much less fogging than their single-pane counterparts but does increase the price! The best paintball masks have thermal lenses