These corrective lenses can be inserted into the new M2004 Intega mask as well as M-211 Freedom One mask. Available in 0.5 diopter increments from -1.0 to -8.0 for left and right lenses. Prescription mask available - Item code: MSK471 Please note there will be an additional 2 to 3 days processing time for most RX lenses Cost is per single lens only Available in Left and Right Negative Diopters: -1.0 ~ -8.0 Positive Diopters: +1.0~+4.5 Compatible Masks: M2004, M2004QB, M-211, M-211QB Returns are not accepted for used lens. Only unused lens are eligible for return with store credit.