They're probably filled with solder.

>>926770
> heat cup
> insert pre-tinned wire
> ???
> throughput of signal

thx, will try it.

I recently did this...and had the same issue. I could not get the wires to go in at all. I was soldering a mini din 9 and couldn't even get a needle through a heated cup.
Intended up soldering to the sides and just hot gluing...

op here. i just checked and there is no solder in the cups at all. and they are very shallow! if the length of the cup (from tip to black plastic body/base) is 7mm, then the hollow part of the cup is only ~2mm. wtf?!

>>926851
Sounds about right, you only need enough to make a solder connection, the strain relief clamp will absorb any cord related violence that may compromise the solder joins.

>>926851
well, 2 mm will be enough for a decent solder joint anyways

/thread
https://www.youtube.com/watch?v=_GLeCt_u3U8

>>926931

thx, i actually watched that before posting. the ones in the video look hollow and have a fillet, the ones i asked the question about look like pic.

op

Maybe there is some kind of female connector that you have to solder to the wires first?

I don't know it just seems like you got poorly designed connectors. In your case I would solder wire into a little coil around each pin and just pot the whole thing in epoxy.