These indicators also known as floats, bobbers are lightweight, small, aerodynamic made of pvc and very bright  in color.

Never dry line nymph, chironomid, midge, or buzzer without a strike indicator. I use the medium size for nymphing and the small for chironomid fishing. Since starting a few years ago using strike indicators my catch has greatly improved, I can keep my fly at the proper depth consistently, and see the take faster. Fish can take and reject a fly without you even knowing it was there, with a strike indicator chances are you will see it.

On still water and streams, never fish without a strike indicator.

For only a few dollars you can greatly inprove your daily catch.

Picture is to show size, placed beside a penny.