Cress loose lens with strength for mask, Big Eyes Evo & Quantum mask to be ordered separately. If your strength is e.g. -2.75 you can choose the necessary lenses either up or down, i.e. to -2.50 or -3.00. -0.25 difference is so small that the eye easily compensates for it. The selling price is the price of one lens. Note! The plus strengths are glued to the bottom edge of the lens - not ground, like in negative lenses. Note! If you order two minus-strength lenses with different strength, remember to mention the desired strength for the right and left eye in the additional information field at checkout. Please note that when choosing lens strengths, the SF number (Spherical) on the customer card received from the optician does not tell the whole truth. Astigmatism (cyl) affects either positively or negatively spherical refractive error correction. You can check the appropriate strength with your optician. Please note that you need strength information for the lens of the diving mask. If