Thumb knurled screw  matched withfixed nut with Spec M8*20,and Finish with Black Oxide to antiHydrogen embrittlement, also this kind of screw made of carbonsteel with Grade:8.8.They are  matched with fixed nut.

You are browsing kinsomhardware.com,where you can find many kinds of non standard  size,style,andsurface treatment of screw,bolts,nuts,and machining parts availablefor customization or ready to buy as is.