This allows me to easily put two swimmers per lane using cords.  One is on this short cord and the other on the long cord.  both can be doing fly without hitting each other.  Since I have only 3 lanes for my team, having the option to have 2 swimmers working cords at the same time really helps out.

i bought these, to use as components, to make my own swim tether.  They are high quality:  nicely made, they float, good stretch and return.  they were shipped very quickly.  well worth it!