The Beyerdynamic DT-102 is a single-ear headphone, allowing the recording artist to hear themselves at the same time as the music that they may be singing along to. The units I have are 400 Ohm versions.
You may also be interested to know that I have a Behringer HA4700 headphone distribution amplifier for sale at the moment.
I have three of these and also two Beyerdynamic DT-100 400 Ohm headphones for sale.
The user manual (and specifications) are available here: https://europe.beyerdynamic.com/dt-102.html
PRICE: £60.00 plus £6.50 p&p to UK mainland. Cost of shipping includes insurance.