Hand Speed Trainer Softball New technology allows you to train swing specific muscles at full speed without changing body mechanics. Easy sizing. Measure diameter of forearm below the elbow. Match to sizing chart. Build strength and improve bat velocity so you can hit the ball harder with better bat control. Includes 2 HST sleeves, 4 8 oz weights, 4 4 oz weights, mesh bag and training manual. 30 day money back guarantee.