Mac Rack II has 8 storage arms and are ideal for transporting conduit, strut, threaded rod, plc. pipe, copper tubing, etc. and an optional storage tray for job site materials. Sumner Stacking Macs accommodate a wide range of material handling needs, and they can be stacked for convenient transportation and compact storage! All three models are interchangeably stackable which yields sizable savings in storage space. To ensure safe and easy stacking, the caster mounting plates have been designed to securely engage when the racks are being stacked. No tools are required as plunger pins are used to secure and release the arms and sides of all of the Stacking Macs.