This is a brand new set of Yamaha HPH-MT5 headphones

High-grade monitor headphones that
deliver a balanced sound faithful to the source. Perfect for in the
studio, music production at home, or for personal listening. Comfortable
monitoring even during lengthy, extended sessions thanks to ultra light
weight 250g hardware.

Drivers

MT5 headphones feature custom
drivers equipped with CCAW voice coils and powerful neodymium magnets.
Made from aluminium wire coated in highly conductive copper, these
lightweight yet powerful drivers provide a wide frequency response of 20
Hz-20 kHz, and deliver flat and high-resolution sound that meets the
demands of professional monitoring.

Other acoustic components

From the arms to the ear cups, all
acoustic components in MT5 headphones have been designed to deliver the
accurate sound possible by completely eliminating extraneous resonance.