This is how you gain those all-important extra millimetres!
Fastener D30, internal is contained mostly within the (Profile) Tube and creates a level 90° connection. That saves space, because, for example, the fastening bracket for a roller conveyor can then be fitted directly to the vertical strut on a frame. What’s more, panels can be fitted flush to a frame without any need for cut-outs in the corners.
The flush connection between Fastener D30, internal and a (Profile) Tube also enhances the look of a construction.

Cap D30 F, grey similar to RAL 7042 - 0.0.629.80