Tube Guide (Click for more Info) The Tube Guide consist of a steel or aluminium or plastic tapered head and an replaceable nylon brush, and it’s used to guide tubes through the sheets and the tube support plates during tube bundles assembling. The nylon brush fits in the tube end, holding pilot firmly in place. TUBE OD TUBE GAUGE TUBE GUIDE NO INCH MM 1/2" 12.70 16 - 18 TG - 1 19 - 20 TG - 2 21 - 23 TG - 3 5/8 15.88 12 - 13 TG - 4 14 - 16 TG - 5 17 - 20 TG - 6 22 - 24 TG - 7 3/4 19.05 10 - 12 TG - 8 13 - 16 TG - 9 17 - 20 TG - 10 21 - 22 TG - 11 7/8 22.20 10 - 12 TG - 12 13 - 16 TG - 13 17 - 20 TG - 14 22 - 24 TG - 15 1.0 25.40 08 - 09 TG - 16 10 - 12 TG - 17 13 - 16 TG - 18 17 - 20 TG - 19 21 - 23 TG - 20 1-1/4 31.70 15 TG - 21 16 TG - 22