These aluminum barrel nuts slide into 5/16” (8mm) awning rails mounted along the top rim of many campers, trailers, and RVs. Stainless steel eye bolts are held in place with neoprene-backed stainless steel washers, allowing you to securely anchor your MoonShade to your pre-installed awning rail. Need a different size awning rail anchor? Check out the ½” (13mm) Basecamp Awning Rail Anchor and the ?” (9.5mm) Awning Rail Anchor . Product Specs Materials Aluminum Cylindrical Nut 0.3125in (7.94mm) diameter by 1in (25.4mm) length Ring Bolt 1.00in (25.4mm) Length Ring Bolt inner diameter 0.5in (12.7mm) Dimensions 8mm Weight .73oz/21g