10 pcs. of tippet rings . You connect them at the end of your leader and you tie a piece of tippet to it. This way you your precious leaders will last a bit longer. And if you want a different thickness of the tippet. In a snap button you connect a new one to it. Tippetrings are useful because if the line will break unexpectedly then preferably at the tippetring. Just add a new tippet and you can continue fishing.
With a little grease they will simply float , so you can also use the system when fishing with the dry fly.