Help! What is this jack hole called?

Hello, this is a shot in the dark because I don't know if this community is open to tech troubleshooting like this, but my colleague and I are baffled by this motorsports headset for which we are creating costum ear plugs. We need an adapter that would enable one to connect a regular headphones 3,2mm jack into this input but don't know what to search for.

It's 4mm wide, seems to have a small "Q" etched into the edge. If this is common in motorsports, can any of you identify it? Thanks.