I buy the PowerBlocks after look through review for what dumbell set would work for my p90x need . after get the product and use it with p90x , I be happy to say that it be quite practical and get the job do . like other people have say , you have to make sure that you align the weight properly when you switch to different weight , but after the 4 week ive be use it , i have never be afraid of the weight randomly fall on my head or fall to the floor . it be durable and everything you would need for p90x , or for any workout routine . bottom line , get it ! you will not regret it .