1. Hexagonal bolts can be devided into A, B, C three levels. A and B levels are refined bolts which used not widely. Generally speaking, ordinary hexagonal bolts, all refer to C-level ordinary hexagonal bolts.
2.C-level hexagonal bolts commonly used in some temporary connection. Ordinary hexagonal bolts used in building structures are M16, M20, M24. Some mechanical industry crude bolts diameter may be larger for their special purpose.
