Borosilicate Glass Narrow Mouth Conical Flask – 100 mL with Rubber Stopper The 100 mL Narrow Mouth Conical Flask is made from high-quality borosilicate glass, offering exceptional resistance to heat, chemical corrosion, and thermal shock. Designed for accurate laboratory use, it features a narrow mouth to minimize spillage and evaporation, along with a rubber stopper that ensures a secure, airtight seal during storage or mixing of liquids.