Kimble 27400 KIMAX Kjeldahl Flasks with Tooled Necks are round-bottomed, long-necked glass flasks used in digesting samples for the Kjeldahl method of nitrogen analysis. These flasks have a reinforced bead at the top. The 300 mL and larger sizes have tooled necks to provide an accurate stopper fit and to reduce the possibility of breakage in use. The 500 and 800 mL size necks are tooled to take rubber stoppers especially made for Kjeldahl flasks. The 10 and 30 mL are designed from ASTM Specification E147 and larger sizes are designed from ASTM Specification E1377, Type I requirements.