A sensing assembly for use in determining if magnetic tape within a single reel tape cartridge property disconnects from a takeup reel within a tape drive during unloading of the tape cartridge, so that the tape cartridge can be removed from the tape drive without damaging the tape media and rendering the tape drive inoperable. The cylinder includes a chamber with a cross-sectional shape like a circle overlapping another circle. The shell is configured for supporting the absorbent structure at the vaginal region. The resulting assembly, which requires no additional annealing, is then planarized to the original surface.