I buy these weight to use with p90x and while they be ok for the price , I can not recommend they for use in p90x because you have to change the weight too often and quickly . I find the plate and the pin to be cumbersome and easily misalign . you can insert the pin and not actually be in the correct spot and then the plate shift while you be do reps. its not so easy to add or subtract weight . if you be just go to stick with the same weight for most of you routine , then these would work fine , but in p90x I be sometimes use three different weight for one three exercise circuit . I get my husband the bowflex dial weight and those be MUCH better in term of ease of switching weight although they be twice the price . I be go to go back to the traditional dumbbell weight for ease of switching .