Round Clear Hole Spacers Keystone Electronics Round Clear Hole Spacers are available in four types of material with clearance holes for #4, #6, #8, and #10 screw sizes. The aluminium spacers feature a clear Iridite finish in accordance with MIL-C-5541 standards, while the brass spacers have a nickel finish in accordance with QQ-N-290 requirements. The insulated types include nylon 6/6 spacers in a natural colour and phenolic spacers manufactured from a natural colour PBE-grade material. Keystone Electronics Round Clear Hole Spacers have an outer diameter of 0.250' (6.35 mm) or 0.312' (7.925 mm) and an overall length of 0.125' (3.175 mm) to 2' (50.8 mm) with threaded or unthreaded options.