My previous, flexible Fitbit band works great for me, but my wife wanted something a bit thinner, so I came up with this. It's a simple, solid arc that fits around your wrist, with a cutout to precisely fit the Fitbit Flex. Customize to your own wrist size! Updated: Click 'customize'. Enter your wrist measurement, in either inches or mm (but not both). Click on the "Solid Band" tab, and tweak the settings until you like it. Generate and print it! There's an option to 'include support' in the model. You should use this, unless you're using software that does a particularly good job of generating support structures inside the hole It will put a single thin "wall" in the middle of the area where the Fitbit goes, which will have to be removed. The Fitbit is a tight fit (pressure holds it in place) so make sure that you clean the support structures out well. Insert the Fitbit Flex by sliding it up into the band, thicker end first, so that the ends are held in place in the holes in the band. The lights should facing the outside of the band, through the wider hole. To remove the Fitbit, press it out by pressing through the smaller hole. Have fun!