The SKB Shock Shock Roto Caster Kit is a roto moulded caster board designed for stacking SKBs 20 Shock Racks. The board itself is constructed from roto moulded polyethylene and features 4 locakable casters for versatile mounting options plus convenient wheels for ease of transportation With its durable construction and convenient features this Caster Kit is the ideal companion for your SKB 20 Shock Rack.