Abstract: An assembly according to the invention comprises an inserter device (10), a penetrating member (7) and a base part (100), where: the base part comprises a surface adapted to be attached to a skin surface, a position adapted to receive and/or attach to the penetrating member, and means (14) adapted to secure the base part to the inserter device, the penetrating member comprises a part to be placed subcutaneously or intramuscularly, a body (24) which is in contact with the inserter device during insertion and with the base part during use, and the inserter device comprises a cavity for receiving the penetrating member, means (45) for accelerating the penetrating member and bringing the penetrating member to the receiving position in the base part and means for penetrating the skin of the patient. The length of the joined assembly (1 total) before use is larger than the length of the base part (12) alone.