A tube assembly of the present invention has at least one subunit with at least one dry insert generally surrounding the subunit which may be disposed within a tube, thereby forming a tube assembly. The subunit includes a fiber optic ribbon and a sheath, wherein the sheath is tight-buffered about the fiber optic ribbon, thereby inhibiting buckling of the ribbon during temperature variations. Additionally, the tube assembly can be a portion of a fiber optic cable having a sheath that may include a plurality of strength members and a cable jacket. In other embodiments, the subunits and dry insert are disposed within a cavity, thereby forming a tubeless cable. Additionally, subunits may include a marking indicia for denoting the security level.