Thank you. 20 used hard tennis balls. How about using them for baseball or soccer practice? They can still be used for tennis practice, but I don't know the manufacturer. There is some fine thread debris attached. ◆ Baseball: Tee, long tee, and free batting practice in a small space. ◆ Soccer: Shooting and juggling practice. (I think it's effective for training to catch the core because they are small) Please enlarge the photos and check them carefully. Elementary school students in the lower grades are afraid of the ball when they first join the team. It's probably because of the fear of "it hurts when it hits you." Using tennis balls (which are similar in size), Catch ball and fielding practice with bare hands. The pain will be reduced even if it hits your body. (Please be careful of finger injuries!) Batting practice such as tee and long tee. The impact on the body is less because of the light weight. ※For reference [Hard tennis ball specifications - From Wikipedia] Diameter (mm) 65.4～68.6 Weight (g) 56.0～59.4 [Elementary school D ball specifications - From the All Japan Soft Baseball Federation HP] Diameter (mm) 64.0～65.0 Weight (g) 105.～110 [Elementary school J ball specifications - From the All Japan Soft Baseball Federation HP] Diameter (mm) 68.5～69.5 Weight (g) 127.2～130.8 The packing box will be a long recycled cardboard box. Please refrain from purchasing if you are nervous, Please enlarge the photos and only purchase if you understand. Purpose...Hard ball