Hollis M3 Corrective LensesHollis M3 Optical Prescription Lenses The Hollis M3 Mask Optical Prescription Lenses are available in Left and Right. These prescription lenses are pre made corrective lenses made from high quality optical glass and are minus power lenses. Left and right lenses are sold separately,Negative Diopters: 1. 5 to 8. 0Available in Left and Right Please check with your optomitrist before purchasing to get the correct strength