Hydraulic line pressure keeps brake secure. No special linkage. Not recommended for use with silicone brake fluid or as an emergency brake. Features 1/8" NPT female on inlet/outlet. Device is generally used to lock the rear brakes. To set the lock, step on the brakes, push the lock knob down, and take your foot off the brake. To release the lock, step on the brake again slightly harder than before and it will release automatically. Warning:This is not compatible with any silicone brake fluid. Kit Includes: (1) Speedway Park-Lok Universal Hydraulic Parking Brake Line Lock. (2) 1/8" NPT Brake Adapter Fittings.