Cross recessed(+)Truss head machine screw(D=8 Large head(Coarse Steel Trivalent white(Silver) 3 X 6 Pitch 0.5

The head has a round shape, like the upper portion of a sphere cut away. Compared to a round head, the height is lower. A distinguishing feature is that the head outer diameter is larger than other head types, which provides a greater bearing surface area and can be expected to offer benefits such as resistance to loosening.

Truss machine screws are relatively common and can be seen throughout everyday settings. Due to their attractive appearance, they are also used as decorative screws, similar to oval countersunk heads. Unlike countersunk types, they do not require counterboring, making them suitable for a wide range of applications; however, the trade-off is a larger head outer diameter.
Machine Screw Head Dimensions Reference　Truss Machine Screw Encyclopedia

• Cross recessed (+) truss head machine screw D=8 Large head Coarse pitch
• Nominal diameter (d) M3
• Length under head (ℓ) 6.0
• Pitch 0.5
• Cross recess number 2
• Head diameter (dk) Nominal 8.1 Tolerance 0,-0.5
• Head height (k) Nominal 2.2 Tolerance +/-0.15
• Cross recess (m) Reference 4.0