Abstract: A multi-layer tube (MLT) to inhibit transmission of water vapor and for flame resistance greater than UL-94 HB includes an inner layer having a melt-extrudable polymeric material including a fluoropolymer and at least one additional layer positioned radially outward of the inner layer and including a flame resistant melt-extrudable polymeric material configured to minimize oxygen permeation. Additional layers may be configured to provide flexibility, oxygen and/or nitrogen barriers, thermal insulation, non-reactive materials, transparency, translucency, structural reinforcement, thermal and/or electrical conductivity, and/or dissipative properties. The MLT may be encased in a bundle cover with another tube element and/or electrically conductive element to form a tube bundle.