Highly visible poly yarn easily attaches to your leader by loop for adjustable depth. Since they are reusable, they are economical. They can also be treated with floatant for a higher ride in the water. Per 4. Colors: Green, Yellow, Orange.
They are easy to use, the color even stands out in the glare of the sun - even that later afternon/early evening silver reflection/glare that your polarized glasses doesn't cut. Obviously not made for real turbulent water but they will pop up when the trubulance allows.
I've only used the poly indicator once. They seem to work great. I had to apply floatant, otherwise it sunk and had to use a half hitch to keep it in place. May have to trim the mini size down under the clear, shallow conditions I was fishing.