I absolutely love these dumbbell . the ease of use be incredible and the ability to change small increment in weight and not have weight all over the place be great . right now I be do some circuit type training that require you to move from one exercise to another with a very short break , these make it easy . I can finish a exercise , change both these from one weight to another and get they in position for the next exercise in under a minute , easily . I have have no problem at all with the quality and use . you do need to make sure the pin be fully seat and both side be under the same weight as many have state but it be no extra effort , just pay attention and make sure the pin come all the way through when you push it in . they be easier to change on a hard surface , if you use a carpeted floor it help to lift one side to change the pin . only negative I can come up with , these do not expand into a heavier set so you may grow out of this set . so think that through carefully as you may save $ $ in the long run by buy the next set up to begin with .