When you have multiple null modem cable lengths but nothing is quite as long as you need, this cable provides a quick and easy solution.
Standard DB9 Null Modem cables have male to male connection ends. In order to connect two of these kinds of cables together, an adapter or cable with female to female ends needs to be used. This cable is 6 feet long and would rest between to standard cables to combine all of their lengths.
This gives you an advantage over buying a single long cable. If you already have a few shorter standard cables, you don't have to waste the money on a really long cable. If your needs ever change, you can always pull the short cables apart and reorganize.