The Dive Optx stick on lenses can be a little tricky. To make sure they stick on, check that the mask is clean from oil and dirt. Then figure out where the best placement for them is on your mask, once you have figured that out hold the lens and submerge the mask in warm fresh water. Rub the lens to push any air bubbles out. Then take the mask out of the water and let it dry/set for 24 hours. Like any adhesive time will create a strong bond.
At any point within the 30 days of purchase, the items can be returned so long as they are still in re-sellable condition. We do not carry bifocal masks, we just have the Dive Optx and Prescription Lenses.