Vintage tennis ball pressurizer. Screw it onto a can of tennis balls and pump it a few times to keep your balls fresh and bouncy. : r/specializedtools
Amazon.com : BALL RESCUER: Tennis/Padel Ball Life Extender – Converts Plastic Tennis/Padel Ball Containers to a 30 psi Ball Pressurizer – Needs a Bicycle Pump to pressurize (Ball Container and Pump not