I normally use the round stoppered releases, but they often release accidentally or don't release, and I'm always wondering how long it's taking for the fly to get down. This solves both. The downsides are a more difficult cast and wind knocks them down. It's hard to understand how they work - they really need to post the instructions found on plumbobber.com. The tubing slides to cover up a loop. First you push it down to expose the loop and thread it on. Then you pull the tubing off and embed the line between the tubing and the peg. When the fly settles at the bottom that slight weight causes the tails to pop up so you know you're down. When fighting a fish the pull of the line will pop the line out from the tubing and slide so you can retrieve without the indicator.

Best slip indicator on the market today. My preference, by far, for fishing deep chironomids.

I recently bought these and like them. They are easy to see and very sensitive. I bought the medium size, and this seems to be about right for the balanced leech and chironomid fishing that I do. I have had some issues getting them to release when a fish is on but feel like that is just a learning curve and they will be great. Haven't had them long enough to judge how durable they are- should last a very long time for the price.