Kastar flexible valve air-hold tool allows replacement of valve seals and broken or weak valve springs on OHV and OHC engines without removing the head by applying air to cylinder through spark plug hole. Kastar flexible valve air-hold tool features a flexible design that makes jobs easier and quicker where spark plug holes are hard to get at, and an overall length 13”, with one end 14mm and 18mm threads fit spark plug hole. Other end 1/4” female pipe thread for coupler plug attachment. After attaching plug and quick coupler, air pressure keeps valve closed while working.