Abstract: A module assembly (1) for fibre-optic distribution, which is mounted along a mounting direction in a slot (11) defined in a carrier unit (2), with a centre region (M) through which a centre axis (A) oriented in the mounting direction (x) runs. Two side regions (S), each of which is positioned opposite the other relative to the centre axis (A) each have a side wall (20.1). At least one of the side walls (20.1) has in certain sections along the centre axis (A), a curvy and/or multi-step profile that changes a distance (d) from the centre axis (A) such that the at least one side wall (20.1) forms at least one protrusion or setback portion (23, 24, SP) for form-fitting mounting a module assembly (1) in the slot (11) defined in the carrier unit (2).