Cylinder head screws Hexagon, also referred to as the inner hexagon bolt, cup head screws, hex screws, the names is not the same, but represent the meaning is the same. The commonly used six screws if there is level 4.8, level 8.8, level 10.9, level 12.9. Also called the inner six angle screw, also called six angle bolts. The head is in the six corners of the head, and the cylinder head. Divided according to the material of stainless steel and iron. Stainless steel with stainless steel SUS202 six screws, this is stainless steel materials, stainless steel SUS304 inner six screws, stainless steel screws SUS316 six. Iron according to the six angle cylinder head screws strength grade points, there are 4.8 angle cylinder head screws, there are 8.8 six angle cylinder head screws, there are 10.9 six angle cylinder head screws, there are 12.9 six angle cylinder head screws. 8.8 level -12.9 level six angle cylinder head screw is called high strength high grade inner six angle bolt. Standard number 70.1-2008 StandardNo:GB/T.