Complex sentence: The USGA (America's governing golfing body) has started testing drivers for COR and has placed the upper limit at 0.83, golf balls typically have a COR of about 0.78.
Split into simpler sentences: The USGA (America's governing golfing body) has started testing drivers for COR and has placed the upper limit at 0.83. Golf balls themselves typically have a COR of about 0.78.