Customers say this shaker cup has mixed performance when it comes to sealing. Many report leakage issues during shaking, despite tightening the lid. The dark, sleek design receives praise, and users appreciate its convenient size that fits well in cup holders. While some find it easy to clean and durable, others mention inconsistent build quality. The cup works well for daily use at the gym, sports activities, and general hydration. Most find it simple to use, though proper lid attachment appears crucial for optimal performance.