One reason its my favorite for mounting is that the small button close to the head makes changing modes very quick, Fenix has been around for awhile now and durability has been great. Here is a short video I took (when I had a cold) that shows how the Fenix TK15 works, Performance is Very Good, this light has the perfect amount of spill to use in a tactical situation or for just general use.
http://www.youtube.com/watch?v=Ksi-I2lqiY8