Proflow Pro Series Secondary Linkage Kit. Featuring Stainless Steel construction and a lightweight yet rugged design, it provides a bulletproof method of adjusting secondaries on all Double Pumper, HP, and Ultra XP carburetors. It allows user to pick between 1:1 or progressive secondary ratio. Kit provides infinite adjustment of secondary throttle blades for maximum horsepower output. Features: Includes all necessary hardware Compact design won't interfere with throttle linkage Perfect for circle track and drag racing Detailed instructions included Simple installation Tough Stainless Steel construction for longevity, durability and control Choose between a 1:1 and a progressive secondary ratio