Product description Massage Lumbar Support The lumbar pillow with a USB cable provides a relaxing massage when you feel tired. Patent Linkage Armrest We have carefully analyzed the reasons for the instability of linkage armrests, and after professional experiments, we have improved their stability. Multifunctional Tilt Mechanism The multifunctional tilt mechanism adapts easily to your needs. Class 4 Gas Cylinder Class 4 gas cylinder provides industry-leading durability, stability and safety. Reinforced Nylon Base The matte black base is made of durable nylon and can carry up to 300LBS. Tilt Mechanism Class 4 Gas Cylinder Nylon Base What are the improvements of LS-6657 series chairs? What is the size of the seat?