RX Mask - Scuba or Snorkel Most stock prescription masks shipped within 24-48 Hrs!
Two lense design, low volume, medium fit, tempered safety glass lesses, swivel buckels, crystal silicone skirt, double-edged facial seal for air tight comfort, easy adjust silicone mask strap, optical are available in diopters from -1.0 to -7.5
NOW -8.0. -8.5 -9.0, -9.5 and -10.0!
How to calculate your prescription or RX for a step diopter lens
OD (Ocular Dexter) refers to your right eye.
OS (Ocular Sinister) refers to your left eye.
Sphere Refers to the degree of correction needed by your eye, measured in diopters.
For nearsighted people this is always (-) negative.
Cylinder Refers to the amount of astigmatism in your eye (the degree by which your eye is not uniformly round).
Get your latest Rx from your Optometrist
For the best result, you must add one half (1/2) of the cylinder number to the sphere number.
Take care to add or subtract correctly
Follow examples below to select RX
Example 1
Sphere, Cylinder, Axis
OD -3.0 0 . 0
OS -2.0 .0 .0
RESULTS RIGHT LENS –3.0 LEFT LENS –2.0
OD : Sphere of –3.0, plus ½ of the cylinder 0 : -3.0 + 0 = -3.0
OS : Sphere of -2.0, plus ½ of the cylinder 0 : -2.0 + 0 = -2.0
Example 2
Sphere Cylinder Axis
OD - 3.0 +.50 .0
OS - 2.0 -.50 .0
RESULTS RIGHT LENS –3.0 LEFT LENS –1.5
OD : Sphere of –3.0, plus ½ of the cylinder +.50 : -3.0 + .25 = -3.25
CHOOSE 3.0 - WATER NATURAL MAGINIFICATION WILL ALLOW - USE ROUND DOWN
OS : Sphere of -2.0, plus ½ of the cylinder -.50 : -2.0 - .25 = -1.75
CHOOSE 1.5 - WATER NATURAL MAGINIFICATION WILL ALLOW USE ROUND DOWN
Example 3
Sphere Cylinder Axis
OD -3.0 +.1.50 .0
OS -2.0 -1.50 .0
RESULTS CUSTOM
OD AND OS HAVE CYLINDER READING ABOVE +1.0 OR –1.0
Wow, I can see down here! 
