3.5mm

Passive 3.5mm jacks

3.5mm is a pair of standard sized TRS jacks with flexible rear-panel headers. Hook your 3.5mm to any intellijel-format audio modules to act as front panel inputs, outputs, or a combination of both! 3hp may seem like a strange width, but this was chosen for good reason - this was the minimum width the hardware fit inside, and when paired with another 3.5mm or a 1/4", you're left with an even number of hp occupied.

https://crey.space/products/3-5mm