is often used by specific manufacturers or resellers (such as Wera ) to denote the same 6-pointed star pattern.
If you are looking at a screw and see a perfect star shape, it is a standard T20 . If you see a star shape with a small metal bump in the middle, it is a security TX20 , and you will need a specialized security bit to remove it. difference between t20 and tx20
It didn't "fit." It wedged into the corners and felt tight. As soon as you applied torque, it slipped because the contact surfaces were mismatched. You got lucky; do not repeat it. is often used by specific manufacturers or resellers