The present invention discloses a system including: (a) a host device including: (i) a cavity; and (ii) a socket, recessed in the cavity; and (b) a UFD configured to be reversibly operationally connected to the host device via the socket, wherein the UFD is configured to physically reside substantially in the cavity when the UFD is operationally connected to the socket. Also disclosed is a UFD system including: (a) a first part having components of a UFD, wherein the components include a primary connector and an electronics assembly; and (b) a second art having a UFD holder and a secondary connector, wherein the UFD holder is configured to reversibly accommodate the first part, wherein a dimension of the first part parallel to an insertion direction of the primary connector is shorter than a dimension of the second part parallel to an insertion direction of the secondary connector.