Clear, low-thermal-expansion borosilicate glass Flasks (Conical) An Erlenmeyer flask, commonly known as a connical flask or E-flask, is a widely used as laboratory flask which features a conical base and a cylindrical neck. They are usually marked on the side (graduated) to indicate the approximate volume of their contents.we produce all our flasks as per the international Standards. base and a cylindrical neck. They are usually marked on the side (graduated) to indicate the approximate volume of their contents. read more