Schematic of filament geometry. The large circle shows the HST-COS aperture, which is a circle with a radius of 1.25″ (101 pc) at the distance of M87. The ambient ICM temperature is T ≈ 2 keV, but there is also a significant T ≈ 1 keV component within our field of view, which we argue is projected in front of the filament and is associated with the other side of the eastern radio lobe. In our model, the filament is a cylindrical structure with a radius r_c ~ 10 pc, containing cold (T ~ 10³ K) clumps with a low volume filling fraction f_c. The clumps are surrounded by thin “skins” or “shells” which are multiphase and contain the intermediate-temperature plasma that produces the bright FUV emission lines studied in this paper.