The 600 Series Mobile Elevated Work Platform (MEWP) Main Boom Lift Cylinder Assembly Seal Kit. This kit includes: Lock ring, hydrolock, piston rod o-ring, piston rod back-up ring, Wear ring, head o-ring, head back-up ring, rod, and wiper seals. The main boom lift cylinder is used on various 600 series MEWPs to lift or lower the main boom assembly through hydraulic pressure. The MEWP Main Boom Lift Cylinder Seal Kit is compatible with JLG models: 600A, 600AJ, 600S, 600SC, 600SJ, 600SJC, 601S, 660SJ, 660SJC. Ensure proper assembly and serial range of machine.