... .standard:by clients 2.size:M20*145;22*170;7/8"*6-3/8" 3.material:carbon steel 4.certificate:SGS Square head ... requirements.2. size: M20*145;22*170;7/8"*6-3/8" 3. grade: 4.6, 5.6, 8.8, etc.4. material: carbon steel5. surface treatment ... : yellow zinc, or by clients (plain, black, HDG, Dacron, etc.) 6. packaging ...