I've tried this product several times and they just plain don't work - my mask foggs up almost immediately. I would not recommend this product.
These towelettes are a great idea. They come in handy during swim meets because they can be used several times over the course of a day.
Bought 1 Foggle anti-fog pack and the towelette was plenty moist to use on my primary goggles and spares. it actually seemed to work! most of the other "sprays" had no anti-fog result after using. I will purchase this again.
This works per application. Opportunity is how to save the cloth for serveral applications without it drying out.