About 4 months ago I lost my original Fitbit charger for my Flex. Because of this, I stopped using the tracker and eventually stopped using it altogether. I forgot until I was cleaning out my litter box around the house and realized it. I ordered this charger and my tracker is working again. I connect it to my Macbook Pro via USB and have had no problems. I also connected it easily via the USB charging box that is also used for my iPhone. The FitBit Flex Tracker fits perfectly into the charging part of the cable and will not fall out.