Callaway Epic Irons feature an ultra-thin, ultra-fast face with an improved
360° Face Cup architecture.

It reduces the rim thickness to 1mm at its thinnest point. 

Because the rim can now flex more readily, and at greater speed,
that allows the whole face to flex faster across a much broader area.

That increases ball speed for more distance beyond the sweet spot.
You get more ball speed on impact toward the toe, toward the heel,
high up and especially down low – the most common miss-hit.