The Schiit Sys is a passive preamp matching the style of the other subminiature products by Schiit.
Schiit's Sys stands for Switch Your Stuff meaning if you have a Modi or other USB Dac and a CD player and you need to switch between the two well here you go the Sys is made for you.
Since this is a passive device (meaning no power needed) the shorter the RCA cables the better.
Inputs
2 x Left and Right RCA (single ended)
Outputs
1 x Left and Right RCA (single ended)
Volume control on front of unit and a push button switch, which if you turn the volume all the way up it can also be a passive switch box.
I do not think there is much more a can add it is just that simple.