The brand new Hallman Pro RX Kit contains the Hallman Pro valve with a ceramic ball, light AND heavy springs, 3 feet of hose, mounting bracket, hardware packet and complete installation instructionst. The Hallman Pro RX Kit is designed to allow very specific control of boost. The RX kit has a ceramic ball instead of the 316 stainless ball that comes in the Hallman Pro and Hallman ES valves . The ceramic ball only weighs a fraction of what the stainless steel balls weighs. This weight difference allows the ceramic ball to act very quickly as it is constantly changing directions during operation. The ceramic ball, in conjunction with the use of a lighter spring will allow very fine adjustment of boost up to 4 to 5 pounds of boost over stock. Boost has been able to be adjusted in half pound increments very consistently with this valve. This kit is specifically designed for turbo enthusiasts that want to add a few psi of boost over stock, and have a great amount of control over those few pounds. This kit also includes the heavy spring for those that would like to switch the spring and adjust to more than 5 psi of boost over stock, and still take advantage of the quick-acting qualities of the ceramic ball.