Heavy, unlathed, air-vented bottom boosts power and crispness for increased clarity and precision. The unique design of SABIAN 13" HH Fusion Hi-Hats in Brilliant Finish also helps eliminate airlock. HH means "hand hammered", the most musical and tonally complex cymbals available. The sound is warmer, darker, packed with tone. This allows HH cymbals to blend into the music, making it fuller, richer ... more complex and interesting.