These bolt kits consist of 4 hex head 18-8 stainless steel M8 x 1.25 bolts x 40 mm long, 8 stainless steel flat washers, and 4 stainless steel M8 nuts. The bolts in these kits are the correct length for bolting together two unthreaded standard ISO-F 63 hole through flanges or fittings. It is recommended to use anti seize thread lubricant on the bolts when assembling connections to keep the bolts from galling or seizing, particularly when the connection will undergo bakeout temperatures (part number P102545). A centering ring with O-ring seal is required and sold separately (part number P101761).