Metaltech SAFERSTACK Complete 2-Section High Tower Scaffolding System, Model# M-MRT5710 SAFERSTACK frame stacks in 30% less space than regular frames, allowing the user to be more efficient when moving to and from the job site Frames interlock for safer storage and transport, helping to prevent stacked frames from sliding Scaffold frames have a durable, long lasting blue anti-slip textured powder-coat finish for superior grip and secure footing when climbing Perimeter tubes 1-5/8in. O.D.(13 ga. steel), interior tubes 1in.(16 ga. steel) Pin spacing is 4ft., the industry standard that&#39;s compatible with most scaffolding