ULTRAVIOLET PROTECTION FACTOR (UPF)
UPF is the rating system used for apparel. It is similar to SPF (Sun Protection Factor), the rating system used for sunscreen products. SPF pertains only to a sunscreen's effectiveness against UVB rays, considered to be the more damaging type of light. UPF, however, gauges a fabric's effectiveness against both ultraviolet A (UVA) and ultraviolet B (UVB) light.