Material : CR - MO (Chrome - Molybdenum)

The "1/2" SQ X 1/4" Tjap Mata Bit Holder" is a Tjap Mata brand screwdriver bit holder adapter that connects a 1/2" Square (SQ) socket wrench handle to a 1/4" hex screwdriver bit.
Here are the product details:
Brand: Tjap Mata (Carl Schlieper, originally from Germany, now acquired by PT. Tjap Mata Indonesia for its trademark in Indonesia).
Main Function: Allows the use of air screwdriver bits or standard screwdriver bits (those with a 1/4-inch hex shank) with tools with a 1/2-inch drive, such as socket handles, ratchet wrenches, or torque wrenches.
Dimensions:
Drive: 1/2 inch Square.
Exit (Bit Holder): 1/4 inch Hexagonal.
Material: Generally made of high-quality steel such as Chrome-Molybdenum (CR-MO) or Chrome-Vanadium (CR-V), designed for strength and durability, including impact resistance.
In short, this tool is very useful for converting a standard socket wrench into a powerful screwdriver.