REGINA CHAIN 520ZRT GB 110RS+RH 135ZRT/1003Z ring chains feature the patented Z44 sealing rings, which greatly improve performance and wear life, making previous X ring and Z ring chains obsolete, 50% reduction in friction compared to traditional O rings, Constant lubrication from special high temperature grease in the critical pin bushing area provides long life, High carbon alloy pins to minimize wear and increased roller thickness to prolong durability, Thicker outer plates and quad