Sealed with LEAK-PROOF PHENOLIC CAPS These modern leak-proof caps eliminate the need of the classic paper/plastic seals that can detach from the bottle neck due to the monomer chemical composition. Phenolic Caps made of industrial-grade highly rigid plastic, molds itself around the sealing areas as the cap is screwed on, virtually eliminating leakage, evaporation, contamination, and forming an exceptionally tight seal. The conical shape of these caps provides an excellent seal across the top of the container and seals across the inside diameter.