Would you believe this little cable does exactly what its supposed to? Power travels from one end to the other! It can power one of your 3.25" floppy drives, i can power your USB 3.0 card, it can power all the things! If you cut it in half you now have two extremely versatile cable ends, not that you would.
I just built a new computer. My new power supply did not provide any Mini-Molex (Berg Plug, 3.5" plug) power plugs. However, I had some add-on PCIe cards that needed this type of power plug. This adaptor solved my problem. It works fine.