GetWetStore BiFocal Gauge Reading Scuba Dive Snorkeling Mask Prescription Lenses Promate Super Scanner Scuba Dive Mask (Rx-Able)/MK450: Bifocal Optical Corrective lenses (also called Gauge Reader) available in +1.0, +1.5, +1.75, +2.0, +2.25, +2.5, +2.75, +3.0, +3.5, +4.0 (gauge reader.)