okay , when you first look at these you get that feeling and ask question like , be they for real ? what be the deal with the squareness ? I ask those same question until I personally see and use these . all I have to say be these be the best adjustable dumbbell out there . yes , the Bowflex one be cool and everything , but personally they be not worth it . they be extremely long , almost double the length of the Powerblocks . for just 10 pound , its the same length even for 50 with the Selectechs . the powerblock be small and be very easy to use . I love how the pin be magnetic and the square shape show how sturdy they be and they be definetly sturdy . they may rattle a bit on some weight but do not be turn off . the weight will never fall off if you make sure you put the pin in the right weight . the main reason I buy these be for p90x and they go together perfectly . do not just go off the negative review until you actually see and use these weight personally . I even get to try out the Bowflex one but the length be a huge turn off for I and I hear they break easily and be a bitch to fix . so , if you be a first time adjustable dumbbell buyer like myself , I stronly recommend the Powerblocks so go down to you local sport goods store and take a look at these .