Our SCBA mask spectacle frame uses polycarbonate safety lenses. Used with a face mask the user retains his vision when the SCBA mask is removed, unlike other frames that mount inside the face mask. The thin rubber temple straps offer minimal, if any, loss of air when using the MAG-1 frame with a SCBA mask. On scene safety is enhanced because the vision impaired work retains his ability to see when wearing the MAG-1 frame. One size fits all.