I decided to do a science experiment for the common good...lol. I've been wearing inexpensive Eastbay Evapor Long sleeve T shirts (and an UnderArmor as well) under my bike jerseys all summer. I do not notice any sun burn on my arms/torso. There are some internet articles about the spf/upf properties of different clothing...one included the Eastbay product saying it tested in the 300s even when wet. Okay, I'll bite, because I already know they seem to protect me from burn on my arms and torso during long rides. These are not bike specific tights, so I'm not sure how they will work (they are fairly thin, so will have to be worn with another short), but at $25 for two, I pulled the trigger and will report back in a few weeks. Btw, they have a 3/4 length.