a fixing arm for fixing to a piece of furniture,

an element for fixing to a door,

a first rocker and a second rocker forming a four-bar linkage and connecting the fixing arm to the element so as to enable a reciprocal pivoting, wherein the second rocker is removably insertable into the four-bar linkage,

a V-shaped spring having a first arm and a second arm, placed around a pin near an end of the first rocker, wherein the first arm of the spring rests on the fixing arm, and the second arm rests in direct contact on a first cam-shaped protrusion of the second rocker, the first cam-shaped protrusion having a first predefined shape, whereby a lever arm is created adapted to compress the V-shaped spring to apply a first force on the second rocker positioned in the four-bar linkage, with the first force oriented in a first direction selected from the group consisting of a door-closing pivoting direction or a door-opening pivoting direction,

wherein the removably insertable second rocker is selected by a user from the group consisting of a first rocker configuration, a second rocker configuration, and a third rocker configuration with differently positioned and shaped cam-shaped protrusions on each rocker configuration, wherein the first rocker configuration includes:

a first shaped member; and

a first insert of a first shape anchored to an end of the first shaped member;

wherein the second rocker configuration includes:

second shaped member; and

a second insert of a second shape different from the first shape and with the second insert mounted to an end of the second shaped metal member; and

wherein the third rocker configuration includes:

a third shaped metal member with a shaped tongue at an end of the third shaped metal member;

whereby, with the second rocker selected by the user and mounted to the fixing arm, a second force is applied on the second rocker, with the second force oriented in a second direction opposite to the first direction.