These 2L PYREX® kettles have covers with openings to accommodate three 24/40 Standard Taper joints and one 34/45 Standard Taper joint. Interchangeable Standard Taper joints allow quick assembly with condensers, stirrers and funnels. Flanges of covers and bottoms are finely ground for a tight seal. For use with heating mantle only. For replacement covers, see No. 6947-2LCO: for replacement bottoms, see No. 6947-2LBO