1000 type for 125 - 500 ml narrow neck flasks for 250 - 1000 ml narrow neck flasks for 500 - 2000 ml narrow neck flasks for 1000 - 4000 ml narrow neck flasks pcs per sales unit. 1. 1. 1. 1. Kjeldahl flask. For nitrogen determination. Made of borosilicate glass LBG 3.3. sales unit reference. NFL3-050-006. NFL3-100-006. NFL3-250-002. NFL3-500-002