Both Pyrex and non-Pyrex tubes are offered. Pyrex tubes are necessary if you need to reopen the tube and do additional glassblowing. The non-Pyrex tubes are ideal for samples that will be archived. In both cases, a 50mm section of 5mm OD tubing is sealed to a 7” sample tube. The extra tubing allows the tube to be secured in the Tip-Off Adapter with ample length for safe flame sealing. A uniform constriction, with a 2mm ID, is placed just above the 7” length.