I need something faster than my adjustable dumbbell -lrb- the plates\/collars type -rrb- for my p90x workout . I could buy the Bowflex Selecttech dumbbell for about the same price as a full set of these in the 15-45 pound range . with these dumbbell , I do not have to worry about they break if I be not move slowly , so if you have the space , these be great . these be probably the best addition I have make to my home gym ... not to mention , I receive these only two day after order , and I do not request any special shipping .