I bought a Fitbit Flex when they first came out, had it for about 10 months and then one morning it wouldn't recharge or turn on, tried everything to reboot and contacted customer service but nothing worked. I decided to buy a Fitbit Zip to replace it and am much happier with my choice. I think the Zip actually gives me a more accurate reading of steps taken. The ones you wear on your wrist will record steps when you are typing on your computer (they tell you not to put on your dominate hand). The Zip if pretty accurate in recording but like most trackers I find that if I am doing strength exercises, yoga or Tia Chia and not cardio it doesn't record movement. The battery in the Zip will last for about 6 months and it will sync to my computer and smart phone so I can keep track anywhere. I wear in the center of my bra and don't have to worry about losing it.