These stoppers are designed to be employed when very harsh chemicals are used, and highly corrosive fumes are generated. 

Features:

• Engineered to hold up under the harshest conditions, including concentrated nitric and hydrochloric acids, as well as highly corrosive nitric oxide fumes.
• Excellent for use with aqua regia solution in both gold and platinum refining.
• These stoppers are an integrated whole, assembled from a variety of machined PVC parts, ABS fittings, and Neoprene diaphragms.
• Precision engineered, each unit requires 21 independent machining operations to manufacture.
• Typical life expectancy of years.
• Diaphragm forms a tight vapor seal with the edges of the beaker. It flexes to form a tight seal despite the variations in beaker dimensions from brand to brand and beaker to beaker.
• Easily inserted and removed from the beaker.
• Includes immersion thermometer and both male and female quick-connects for a hose connection to a scrubber (scrubber sold separately).
• Available in two sizes.  The AR2L Beaker Stopper fits 2-liter beakers, and the AR5L fits 5-liter beakers.