Klein hex keys are the tools professionals cannot afford to be without Heat-treated and tempered for superior strength and durability Hex ends are square-cut for a secure full-depth fit and maximum contact with the hex socket to prevent slippage and stripping of the socket Handy sets fit your pocket or tool box easily and help eliminate the lost-key problem Tough heat-treated alloy steel Hex-key ends are square-cut for a secure full-depth fit and maximum contact with the hex socket to prevent sl///-Tools/Hand Tools/Hex Key Sets