Made of 4130 tubing, our round lower bar, professional design is lighter - yet stronger - than older models. Spring-loaded assembly is 52" long, with 4"-diameter wheels. Mounts are fully adjustable for varying suspension widths. Our wheel-bracket design lowers the upper bar, greatly increasing bumper clearance on low cars. Installing a full X-strut in the upper bar increases strength and creates more clearance for floor jacks (by eliminating a wheel-separator tube). The upper-X assembly is shipped unassembled to allow for different widths.