Created specifically for ultra high horsepower Pro-Mod type race cars, this Magnum Series 4-Link will withstand the punishment these cars dish out. Each kit includes 1/4'' thick housing and frame brackets (most competitors kits have 3/16'' brackets) with 5/8'' mounting holes on a 21'' radius, as well as 1-1/4'' holes for additional tube gussetting. Directly-threaded links won't hold up under these conditions so we designed special threaded tube inserts that weld into Chrome Moly Tubing. We use a 1-1/4'' o.d. x .095'' wall top tube and a 1-3/8'' o.d. x .095'' wall bottom tube to handle the shock loads without flexing. All hardware and mounting instructions are included to ensure an effortless installation. Requires 3/4'' Thread x 5/8'' Hole Rod Ends. Welding required.