... teeth bottom has no plane, and usually is used with nut.2. The thread teeth angle ... world. But it is still widely used in the market now.Remark: DK screw head diameterK: height ... by Japan, DIN by Germany, ISO international etc.Often used head type (HEAD):BINDING, BUTTON, BRAZIER, FLAT, ... OVAL, PAN, RPUND, TRUSS, HEX etc.Often used driver type (DRIVER):PHILLIPS, POZIDRIV, SLOTTED, TRIANGLE, SQUARE, ...