> does anyone know the actual part number at ProMa for the rails which i
> can then bung some m3 nuts in that's much better than having the long
> thread inserts since i mix manufacturers a lot.

Look at the ProMa website > PRODUCTS > HOUSING PROFILES > 19 Inch Carrier
Frames > 19 Inch Carrier Frame 1

The order no depends upon the length

Best wishes
Dieter Doepfer