The injection device comprises a housing designed or suitable for manual gripping, a container for a preparation attached/enclosed in the housing, an outlet for the preparation exposed with respect to the housing and a mechanism arranged for moving the preparation at least from the container through the outlet. The system comprises a set of at least two elements having different properties in at least one respect. The elements are designed for mechanical attachment to one and the same area part of the housing, one at the time. The method includes the steps of providing at least two elements having different properties in at least one respect, the elements being designed for mechanical attachment to one and the same area part of the housing, one at the time, selecting one element from the set, and attaching mechanically the selected element to said area part of the housing.
