I have tried both the Klarus and Nite Ize ones, and they both have their pros/cons.
Both the Nite Ize and Klarus hold the flashlight on one side or the other. The Nite Ize is nylon webbing that uses velcro to adjust to the size of your head, whereas the Klarus is an adjustable elastic band. The Nite Ize flashlight holder is tighter and wider elastic making it more difficult to put in/take out the flashlight, but once in holds it tighter. I think the Nite Ize is better if the flashlight you intend to use is heavier or longer. Because of the all elastic band, I think the Klarus would be better if you are more active and using a flashlight that is not to long and heavy.
Nitecore also makes one that I have not tried, but looks like it could be nice. The Nitecore is elastic and has the headband piece plus a piece that goes over the top of the head. It has three flashlight holders so one can be on either or both sides and/or the top piece.
