Cast 316 grade stainless steel fittings for making complete guard rail systems. O.D or 22mm (7/8") O.D tube. All have S/S grub screw retainers. The Bases are countersunk drilled. Available in 2 sizes - to suit 25mm (1"). 25mm size for 6mm fastenings. 22mm size for 5mm fastenings. The tube fits internally.