To assess the breathability of the fabric, the evaporative resistance, RET (test based on the ISO 11092 standard), is measured. The lower the fabric's resistance, the more water vapour generated by physical activity can escape, and the higher the fabric's breathability. For example:
RET < 9 = extremely breathable fabric
9 < RET < 12 = very breathable fabric
12 < RET < 20 = breathable fabric
RET > 20 = little or no breathability.
RET of this cape = 8