Many automatic transmissions build up internal pressures that can force the stock dipstick out of the tube and allow automatic transmission fluid to escape. Loosing this fluid can destroy a transmission and create a mess of leaking fluid everywhere. The Aeroflow locking dipsticks counteract this with a locking mechanism on the top that prevents the expulsion of the dipstick handle under extreme transmission pressure. The solid hard tube dipstick allows you to check and fill up the ATF fluid quickly and easily. Each unit includes a locking dipstick, dipstick tube, and rubber tube seal.