Today I went and bought some screws that I needed from a local hardware store (see picture at bottom). By rule R7c it states that
any commercially available #4, #6, #8, M2, M2.5, M3 or M4 screw up to 2'' long (nominal), and any commercially available nut and/or washer to fit these screws.
My problem is that the screws I ended up purchasing did not declare itself as any of them. What kind of screw is this, and will I have to switch to a different type?