XX True Wireless headphones with true deep bass sound by 12mm driver units, tornado shaped ducts and extreme deep bass ports. HA-XC90T deliver true deep bass sound more than ever by the dynamic driver unit with acoustical design. The independent acoustic chamber in the large 12mm driver unit protects the sound from the acoustic adversely affecting battery and electric circuit board. Extreme tornado duct in the independent acoustic chamber are used sequentially, continuingly to control the movement of the diaphragm properly. Extreme Deep Bass controls the back-pressure in the housing to make the most of the driver unit's performance. XX true wireless headphones are powered up with a TRIPLE PROOF included IP55 rating, which strong against sweat, water, and dust.