They are from various firearm aftermarket manufactures, they are all basically the same just different colors of poly I think I have orange, black, and translucent blue. More than once I have forgotten I have them and bought them while purchasing other parts. I also seem to always buy a package of 2 or 3 thinking I'll use them or give them away.
I think I still have one that is poly tubing around a steel pin like Kazoo posted as well.