The tennis trainer's base has a valve for putting sand or water into it to increase the weight so as to provide stable support for training, help to perfect skills of tennis. We truly believe we make some of the most innovative products in the world, and we want to make sure we back that up with a risk-free ironclad 30 day guarantee. If you don't have a positive experience for ANY reason, we will do WHATEVER it takes to make sure you are 100% satisfied with your purchase. Buying items online can be a daunting task, so we want you to realize that there is absolute ZERO risk in buying something and trying it out. If you don't like it, no hard feelings we'll make it right Money Back Guarantee: If your items arrive damaged or becomes defective within 30 days of normal usage, we will gladly issue out a replacement or refund. We have a team of live reps ready to help and answer any questions you have within a 24 hour time frame, 7 days a week. We have 24/7/365 Ticket and Email Support. Please contact us if you need assistance. If you have problems with the purchase, please notify the customer service
