I have a number of sizes of hollow mandrels or blowing tubes. Sold as an individual mandrel. Based on outside diameter (all are 25cm long) 3mm (thin wall) 3.2mm 4mm (thin wall) 4.8mm 5mm (thin wall) 6mm (thin wall) 6.35mm (Australian made) 6.35mm (USA made) 7.9mm (USA made) 8mm (Australian made) 9.5mm (USA made) 10mm (Australian made) 12.7mm (USA made) Thin walled hollows are not suitable for leaving in the flame for mixed oxy torches. If you use only the tip or just a hot head these are a good option. Astrid Riedel's class and tutorial supply list calls for 3-4mm and 6mm diameter by 12" length Stainless Steel Tubing. The fractional equivalents are 1/8" (3.2mm), 5/32" (4mm) and 1/4" (6.35mm), respectively. The following tutorial shows how to use a hollow mandrel or blowing pipe for Vessels
