They DO NOT block out the glare. On a sunny Arizona day in the late morning I cannot see the service line on the other side of the net. That is the dilemma with non polarized lenses. I then tried Maui Jims which I LOVED for blocking glare but I didn't do well with Polarized on the court. I kept my Maui Jims for driving and love them every time I put them on - just not for tennis. In the end I bought non Polarized Oakleys. While they were expensive, the clarity I have across the net (reading the opposing player) is far superior. I hope this helps someone spend a LOT less money than I did to find the right sunglasses. If you don't live in an extremely sunny place, perhaps the experience would be different than mine.
I love these glasses! They block out glare and do not fall off your head when playing vigorous activities such as tennis. I would recommend these glasses to anyone who wants sunglasses that are really a great deal!
Some sunglasses are too dark to play golf and tennis. The lens in these sunglasses lets in more light and can adjust to the light conditions.