Definitely the most popular fly fishing indicator out there at the moment.
These bobbers are very simple to use. Just unscrew the top, lay your leader through the slot and replace top. To adjust, simply loosen screw top, slide where you want and tighten down. The 1/2" is great for casting 3-5 weights without much recoil going back and forth, whereas the larger sizes can feel chunky. The 3/4" is perfect for 6-8 weights. The 1" and 1 1/4" are useful for turbulent water, super weighted flies and heavier rods. You can expect to pay slightly more for these, however our experience is that they last much longer than everything else out there. Plus you don't kink your leader.