Hex Socket Head Cap Screws Bolts and Nuts and Washers Kit: The inner hexagonal cap design can be easily installed with a hexagonal wrench, and it is not easy to slip out. Hex Nuts & Flat Washers: Hex nuts can make your installation more precise, fasten better, and carry larger loads; flat washers can increase the area, protect the bolts, prolong the life, provide strong holding force and maximum clamping force.
eBay