Distinct emission excesses around, and approximately coaxial with, bright radio jets were mentioned at Green Bank (Bridle 1984; O'Dea & Owen 1984). New evidence for this phenomenon was shown here for several sources. (After much debate, a group of the observers at this meeting agreed to call such features ``sheaths''-unwittingly reinventing the term used at Green Bank by O'Dea & Owen!)
Rudnick & Katz-Stone (these Proceedings) used ``spectral tomography'' to show that the jets in the FR I radio galaxy 1231+674 have two spectrally-distinct components with different transverse scales. Varying proportions of ``inner jet'' and ``sheath'' account for spectral gradients that would otherwise be attributed to aging. As well as providing new evidence for FR I jet sheaths, their result emphasizes the importance of exploring multi-frequency visualizations of both intensity and spectral index before choosing how to model the spectral properties of radio sources.
A miscellany of aligned ridges, filaments, rings and some diffuse emission was noted within a few radii of two FR II jets-Cygnus A (Katz-Stone & Rudnick 1994; Rudnick & Katz-Stone, these Proceedings) and 3C353 (Swain, Bridle, & Baum, these Proceedings). The reality of these features is clear, but searches for intensity, spectral, or polarization relationships between such putative ``sheath'' features and the jets (see Swain, Bridle, and Baum) are needed to test whether they are truly jet-related. Such relationships might also distinguish whether sheaths visualize an outer scale of the FR II jet outflow, or a distinct inner scale of the lobe/cocoon/backflow. The latter possibility might alleviate the ``counterjet candidate" problem in the 3CR quasars, if some of the detections are backflowing sheaths, not outflowing counterjets.