Phidgets TSL4211_0 T-nut PG40 M5
The T-nuts provide an option for an attachment point that can be installed in the center of an extrusion without having to push the nut all the way in from the end. This allows for faster installation as well as installation after the structure is fully constructed, but it requires a little finesse to install properly. These nuts are suitable for use with M5 bolts.
Manufacturer Datasheet Phidgets TSL4211_0 (2.21.10.M5)