Update on these pratice tools bought a pair in 2015 they're 2 pounds the biggest powerwrist builders made and have been using them for 6 year's now and was originally at 200 bpm started using them thirty minutes a day and increased it up to an hour a day I have noticed incredible progress in swiftness; endurance stamina... I am up to 250 bpm actually faster quicker than that... these powerwrist builders are incredible.. am very thankful to have them... thank you guy's at powerwrist builders for creating such an incredible ingenious drumming tool...