Straight Tube – Aluminium The Patented APA2013206315 straight tube system is ideal for large projects and very easy to install. The base price indicated is for the smallest pipe and insulation size 15A25T which is not available in Australia. Minimum size requirement a total of 75mm diameter. Important: Accurate pipe size measurements and the R rated insulation used, all sizes must be indicated and the total circumference must be supplied . Please check before ordering.