For years, thingamabobbers have been my go-to strike indicators. When I'm expecting truly subtle strikes and need something very sensitive, I'll reach for yarn, but otherwise a bobber is typically what I'll choose. They're ultra-visible, float as high or higher as any other indicator I've used, and they're easy to attach and remove. But they're not perfect. They often slide when used on thinner pieces of leader or tippet and when used on thicker material, typically leave the butt section of your leader kinked and twisted beyond repair.
This past year, Rajeff Sports introduced a new strike indicator, Air-Lock, which we've quickly accepted as the better bobber. The company that designs and manufactures Air-Lock strike indicators -- a small company based in Portland, Oregon named Field Systems Research --recognized the faults the existing bobber designs had and set to task at fixing them. The solution started with a prototype fashioned out of the top of a toothpaste tube. The eventual result, Air-Lock's screw-on cap design, eliminates both of the aforementioned issues of slippage and kinking.
Air-lock strike indicators accommodate leader and tippet material of widely varying diameters. We've used them on everything from 25 pound butt section material to 6x tippet. Thanks to the o-ring in the cap design, even thin diameter tippets don't slide through once the cap is locked down. Adjusting the position of the indicator on your leader is as easy as twisting the cap a half turn, sliding the indicator, and locking it back down. Once the indicator is removed removed, the leader emerges unscathed.
Like other bobbers, Air-lock indicators are available in multiple sizes and colors. There are sizes for small spring creek nymphing and sizes for working big burly rapids, 3/4", 1", and 1 1/4" are available. Colors are the usual yellow, pink, orange and white.
If you're willing to give up the convenience of being able to remove your indicator without removing your fly (i.e. you know you're fishing a dedicated nymph rig for the day), we know a few anglers who like to take advantage of the Air-lock's design to drop their nymph off their indicator at a 90° angle. This is accomplished by threading the leader or tippet through the center of the screw-on cap before placing it in the grooved holder and fastening the cap. The result is a rig that, in certain situations, is more adept at getting your fly down quicker and one that allows the angler to know with a much greater degree of certainty where his nymph is drifting in the run being fished.