It never fails. Every time I try to pull the chain to turn of my light, I pull the wrong chain and turn on the fan. Then I have to count how many more times to pull it to turn the fan off by stepping through the speed settings. Now I don't have to worry about that problem. Just replace the existing fob on the end of the chain with this one and you will always know which chain is the fan. I made mine out of GID so it is easier to figure out in the dark (though the pointy things should be a give-away). There is now an updated file also (version 2.0). I shortened the blades and made them a little wider so they dont feel so sharp. I will be uploading a picture of the second version (pink PLA) The Light version is: http://www.thingiverse.com/thing:116330/ I made this to be a quick print. No supports, no glue, and no assembly required. Just print it and use it. The standard ball chains used on light switches will clip into the top of the pull. I did have to use a little force to get the 4 balls to clip in, but that was made that way, so they wont easily become disconnected. I printed mine at .20 layer height and 10% infill.