Our 3″ x 6″ shape is the largest shape available. It was created for structures that require very high load requirements. The 3″ x 6″ shape is ideal for heavy duty machine bases, support structures, stairways, mezzanines and anywhere where maximum structural strength is needed. The 3″ x 6″ shape also has four hollow centers that will accomodate multiple air manifolds. Pressure up to 150 p.s.i.