High-Density qwikTRAK floor track shelving can help to maximize storage capacity in a given area. Mobile units are positioned between stationary units and an active aisle can be opened between any two units as needed. This efficient utilization of space addresses the storage needs of growing operations and may eliminate the need for facility expansion or renovation. Floor tracks compensate for rough or choppy floors and provide a smooth, level surface to guide the mobile units in a straight line. Mobile Unit Kits include four 74" (1880mm) high mobile posts, four casters, donut bumpers, and other hardware to assemble a mobile unit. Shelves are sold separately. Casters feature an acetyl grooved wheel and stainless components.