Even in simple patches with only a few modules involved, you often have to sum up individual signals: You need a mixer or maybe two and please as small as possible.
∑42 (pronounced: SUM 42) is a compact and flexible eurorack-mixer and probably the one you are looking for. You can use it as two 4-in-1- or as one 8-in-1-mixer. And of course, it can handle audio-signals as well as control voltages.
∑42 is an indispensable tool with a perfect size-usefulness-ratio.