after much research on adjustable dumbbell I end with the Powerblocks . I try several adjustable dumbbell at the store but nothing can come close to these . I be very pleased with these as they be very functional and quality make . adjust the weight be very fast and easy . they take up very little room compare to traditional dumbbell . if you want easy to use adjustable dumbell , quality make product , and save space than these be the Ultimate Dumbells for you .