THESTACK HARDWARE: 5 milled Stack weights enable 30 weight combinations between 0g and 400g Dual-purpose weight case / phone stand Highly engineered training bat - Pro or Youth version Integrated Stack Sensor measures bat speed, Seamlessly connects to TheStack App Integrated Stack Sensor: No charging required, battery life > 1 year THESTACK APP FEATURES: Customized and responsive speed training formulated by renowned biomechanist Dr. Sasho MacKenzie Guided workout timer for reps, sets, and rest intervals Custom Bat Speed and Distance Potential metrics to track your gains Connect to Coaches and other Players in TheStack App Requires iOS 15.0 or later. ADDITIONAL DETAILS: