The brake pad slider pins can sieze up making them quite difficult to remove.
In many cases siezed pins can "Round off" the inverted Hexagon Allen head making successful removal a hit or miss affair with the risk of damaging the caliper.
These hardened coated steel replacement pins allow easy removal as well as providing a smooth surface for the pads to move freely on.
In most cases one pin is needed for each front caliper however some rear calipers require two pins.