Cowboycool Replacement Large Size & Small Size Wristband with Clasp for Fitbit Flex Activity & Sleep Tracker (NO Tracker) (Black & Teal, Small) Exclusively for the FITBIT FLEX Wireless Activity Bracelet, here is a replacement wristband. Most original wristbands become worn or grubby over time, well they are worn a lot, and you exercise in them ! Made from the Same durable, waterproof materials, these are great replacements for the original wristbands, and great as a spare. With the viewing window, to keep you moving ! So here is an affordable replacement wristband for the fitbit FLEX.