QA1 64-72 GM A-Body Lower Boxed Trailing ArmsAll upper tubular and lower boxed trailing arms use polyurethane bushings on both ends, while upper adjustable and lower tubular trailing arms use a spherical ball or rod end assembly on the chassis end to eliminate bushing bind, allowing the suspension to move smoother for better control. This keeps the tires planted firmly on the ground for improved traction and a more predictable, better handling car. For a long lasting finish, tubular and boxed