The 500 and 1000 mL kettles have interchangeable covers with four openings to accommodate 24/40 standard taper joints. Kettles of 2000, 3000, and 4000 mL capacity have interchangeable covers and have openings to accommodate three standard taper 24/40 joints and one standard taper 34/45 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.