Vertagear Racing Series Ergonomic Office Chair, Black/Green (SL4000) Reinforced 5-Star Base  Redesigned and constructed from a heavy-duty alloy material that assures a solid structure. Effortless Assembly  Slide-in design creates a quick one-person installation process. Steel Frame and High Density Resilience Foam Custom racing stylist Penta RS1 casters coated with PU for soft and smooth gliding on any surface Cushioned and contoured to the shape of the arm with adjustability in 4 directions