These Sand Bag Weights are Constructed of Premium 900D Nylon Material Sand Kettlebell is perfect for Strength Training. Upgraded 900D Outer Construction - Stronger Material vs. Competitors. Upgraded Closure with Hook & Loop Fastener To Keep the Sand Inside the soft kettlebell bag. Hook & Loop Closure Virtually Eliminates The Sand Leakage That Occurs In Other Sandbag Kettlebells / Sand Weights. Upgraded Stitching to Increase Strength. Size 7x7x7 Holds Approximately 15lbs - 25 lbs Depending on Material Used to Fill. Comfortable, Safe, Ergonomic Kettlebell Handle Exercise on Your Time, Where You Want. Just Fill with Sand. Kettlebell Workouts Are A Great Way to Increase Fitness Levels. Take Your Workouts On Road With You! Great For Home Gym Or Traveling Gym! Please Note: Product Ships Empty, Sand Can Be Purchased At Most Home Improvement Store For Around $4 For A 50lb bag.  These can also be filled with pebbles or rocks.