Jeep JK Stage II System with HD X Series arms, The JK 4 inch Stage II systems maintain a lower roll-center for unparalleled off road stability, superior articulation and excellent on road performance. The lower arms are fabricated from laser cut 3/16 inch thick steel plate for outstanding durability and come equipped with aerospace grade high angle rod ends and long lasting polyurethane bushings. Adjustable length front upper arms are included to optimize pinion angle and alignment specifications.