Back to Back Half Slotted Stainless Steel Strut. (Holes are 5/8 inch x 1-1/8 inch on 2 inches center to center.) Back to Back Strut is two standard struts that have been welded back to back for a variety of non-standard applications. Strut channels for framing and mounting applications in outdoor or highly corrosive enviroments, non-rusting. 304 Stainless Steel Half Slotted Back to Back Strut Channel Height: 3-1/4″ Width: 1-5/8″ Thickness: 12 ga. Length: 24 inches Hole Size is 5/8 inch x 1-1/8 inch on 2 inch centers.