Used Hard Tennis Ball Pressure Recovery Maintenance Device Product Name: BALL RESCUER Purpose: Pressurizing hard tennis balls Function: Device to extend the life of balls I used it, but it's been gathering dust in my closet recently, so I'm offering it to someone who needs it. There is no instruction manual, so please refer to the product pages of KPI and other retailers for usage instructions. One unit holds 4 balls. Since there are two units, you can store 8 balls. If you play on an omni court, the felt doesn't wear down much, so if you can maintain the air pressure with this product, you can maintain your balls cost-effectively. The price has recently increased, and this set (3 items in total) currently sells for around 23,000 yen. It also seems to be a popular product that sells out quickly and is often out of stock. Usage: Hard Tennis Wilson Yonex Head Prince Dunlop Babolat Nike Lacoste Tecnifibre Gosen Solinco Luxilon Asics Puma New Balance Alcaraz Nadal If you like these, please consider it.