It's a darker version of the original Breeze Dark with red instead of blue. It works on GTK 2.0, 3.0, 3.18 and 3.2. I tried it on Gnome and KDE Plasma, it works well.
See my profile for more Red Breeze Dark themes.

Cinereus (alternative GTK theme similar to this): https://www.opendesktop.org/p/1280788/