One bad thing about the Bowflex Dumbbells that users complain about is the length of the dumbbell. Well, this is just a minor issue because it can easily be solved by you alone. For certain exercises, the length of the dumbbell is a bit longer and in return, weight lifters need to adjust the exercises to cope up. Some say that by doing the concentration curls, they do it one arm at a time. Others report that they have no problem in using the dumbbells. Well, this is really subjective as it depends on the one using it. But overall, bowflex dumbbells are satisfactory and customers say they did the right thing in buying these products.