This is a breakout box for the direct outs of the TexMix (only versions 1.5 and 1,6 of the channel expanders have the direct out header). 
Each module has 8 outputs so it could have connected two '4MonoChannels' or one '4StereoChannels'.

Without connecting the ribbon cable it's a 3,5/6,3 adapter.

https://www.tesseractmodular.com/eurorack-modules/douts

• 6hp
• Module does not draw current
• 30 mm deep