Hydro-Tac Stick On Magnifying Lenses are stick on prescription powers equivalent to your add or reading prescription. They use static electricity to cling to the backside of your sunglasses, goggles, or other sports eyewear. They are less expensive than regular bifocals, and they offer the advantage of being removable and re-useable. These are perfect for sports as you can put the bifocal segment wherever is most comfortable for you and move it for each individual sport.
For instance, golfers need to bifocal to read a scorecard. However, traditional bifocals are fit so that when the golfer gazes downward toward the ball on the tee, he/she may "catch" some of the bifocal segment distorting the view of the ball. With the press-on bifocals, the segment can be placed to the far right or left side of one lens only so that you can gaze over to read the scorecard, but your line of sight to the ball or the green will not be interrupted.
Or, cyclist often ride with their gaze down toward the street. However, traditional bifocals are fit so that when a rider is on his/her bike looking downward, the bifocal segment is directly in the line of sight. However, with the press-on bifocals, you can place the segment way down low at the bottom of the lens so you can read a map, but your view will not be disrupted.
The press-on bifocals can fit on any lens surface including swim goggles and dive masks. You can remove them when you don't need any near vision. Press-on lenses won't harm the "carrier" lens, because hydrostatic pressure makes them cling. Never any glue or harmful chemicals. Just plain water, that's all. Upkeep is minimal. Warm soapy water keeps them clean. Made by Optx 20/20.