EN 13758-2 is a product standard that protects the skin against the sun's harmful UVA and UVB rays. Clothing that is certified with this standard is marked with an ultraviolet protection factor (UPF-value), which indicates the level of protection provided. The level of protection depends on multiple factors, including the fabric's thickness, density and colour. However, the fabric's protective effect is impacted by wear and tear, and when the clothing is stretched.