Because of a Trim Head Screw`s small head size, there is not much material to support the driver bit. Therefore, the quality of the screw really becomes important. These screws are heat treated steel, and the recess is particularly well formed. Even so, it takes a light touch to avoid driver bit slippage or screw head breakage. Takes a #1 square drive bit. Head Diameter is 7/32 inch. Made in Taiwan, Korea, or Japan.