This is a tube of black urethane automotive glass adhesive, identical in formula to that used by the factory by Fiat and Lancia to glue-in windshield installations in Fiat X19, 128, Lancia Scorpion/Montecarlo and Beta. Used for rear window in Lancia Beta Coupe.
Applies with a caulking gun into the window channel, and the glass is then laid on top of the bead.
Typically requires one tube per glass panel.
This is not plain old caulking! When cured, the material becomes rock hard and practically uncuttable like the original material and securely bonds/seals both the steel channel and the glass.
Don't be tempted to use cheaper silicone caulking or roll-style adhesive, as it will not bond to the glass correctly and will NOT prevent leaks!
The stainless trim ring is also secured to the car with this adhesive.