Which tool to loosen these bolts (multipoint / spline?)

[TonyRPH]

I need to adjust the striker plate but I'm not sure which tool is required to loosen these bolts?

It's definitely not Torx.

I found this set on Amazon - advertised as a 'Spline socket set'.

Is this the correct tool? I'm puzzled as the listing also makes reference to Torx?

Image for reference (this isn't the actual car which is an 02 Audi A3 - 8L) but this looks similar.

[John87]

That set looks right to me. I had to buy a triple square bit set to tighten the same part on my mk1 Leon about 20 years ago as the door wasn't shutting flush

[Ryyy]

Looks like spline bolts to me. Had them on my caddy.

[TonyRPH]

Thanks, I bought a set.