3.5" stereo splitter . Splits sound to two headphones without any sound issues.
I brought this to share music & movies with my wife while enduring an 8 hr plane ride. The unit was plugged into my samsung s7e and the other leads went to our head phones. Everything worked perfectly, but I removed one star only because the plug that sticks in my phone was so big that it couldn't make a proper connection without removing the phones case. It was an inconvenience for me to make it work properly.
Great Service by Monoprice but this product is not good. It keeps loosing the connection from one or both channels. I detected it within few days of the delivery and informed Monoprice. They promptly replaced but the replacement unit is also not great. It seems the design/product (Chinese ?) itself is bad, so stopped complaining.