the comparison I want to start the p90x program and need a set of dumbbell that would not clutter my small apartment living room . prior to purchase the PowerBlock Classic , I read many review on Amazon.com for other adjustable dumbbell as well as this one . I even go to sport store -lrb- Sports Authority and Sport Chalet -rrb- to try they display model . Sports Authority carry the Select Tech -lrb- 50lb adjustable one -rrb- and the Gold 's gym set . both be problematic . I instantly know the Select Tech dumbbell from Bowflex be poor quality when I pick it up . only one of the dumbbell I could pick up because the other be break ! I have use the Bowflex 90lb version my brother purchase and those be much better quality and work fantastically except with the huge setback of SIZE . they be enormous and cumbersome to lift , often clunk together . the Gold 's Gym dumbbell involve a troublesome slider pin that I could not get use to . I come across a few other similar dumbbell with this pin mechanism and most of the pin get `` stick '' . finally , I come to the PowerBlock Classic . the review the PowerBlock Classic be simple , odd-looking , but excellent . I be scare the magnet\/pin lock mechanism for these dumbbell be weak or fragile -lrb- it really do not look like it would hold -rrb- but boy be it sturdy ! for the other reviewer who warn of the danger of misplace pin , I say that it be not a problem ! the pin snap into place so you know that the pin have be properly put in . sure , the pin can get awkwardly stick into the other slot if misplace but as soon as you try to `` snap '' in the pin , you 'll know you have it in the wrong slot immediately and you can correct for this . I have be use these dumbbell in intensive move and slow move and at all sort of angle with no worry of a pin slide out . these feel very solid with no rattle whatsoever . also , I love that the size of these block be relatively the size of you standard gym dumbbell in term of length so that the dumbbell do not clunk together during a bicep curl . I also love how fast and smooth switching plate can be with these because unlike the Bowflex SelectTech and some other dumbbell , you have to `` fit '' the plate into the other plate . -lrb- just imagine that the underscore be empty spot for a plate and the | be plate . | _ | | -- | | _ | with the SelectTech you have to match the plate back into it be exact spot which take a fairly steady hand to do quickly . this be a slight nuance that I get annoy of but may not be a problem for you . -rrb- with the PowerBlock you simply stick the whole thing into the middle of the remain plate which make it very simple and quick for swap weight . the PowerBlock dumbbell be very comfortable to use with a soft grip so you do not need glove . the extra handle I do not really use but they could come in handy . you can even use these dumbbell as push-up stand since they be that sturdy . conclusion i buy these from Sport Chalet for $ 300 + tax which come out to something like $ 330 so that I do not have to pay for a huge shipping fee . I highly recommend that you get these if you want a set of space-saving adjustable dumbbell . I would say these be the best on the market in agreement to another reviewer .