The 1321 has hinges pre-assembled.
The same hinges are used for inlay or overlay doors - it depends on how the slides are set up during installation.
With the 1321, the slide is mounted 'inboard' of the door, on brackets.
In most of the other systems, the slide is mounted 'outboard' of the door, on the carcass.
For inset or overlay, and depending on the door thickness, you then position the slide as per the installation guide.
Overlay = slide moulding flush with carcass front & slide positioned on moulded scale
Inset = slide moulding inset by door thickness +1.6mm & slide positioned on 1 1/2 mark on the moulded scale.
Please see installation guide for details.