I tan way too easily.  Going outside for 5 minutes in the summer will result in an arm tanline.  After several months of this my arms look a mess.  I've been using this shirt to take care of my flower beds weeding,  dead heading,  etc...  I use it over whatever t-shirt I'm wearing at the time with a hat.  I haven't gotten any crazy arm tanlines since using this shirt.  It's also very lightweight. Although long sleeves, it doesn't make me hot when wearing it.  I highly recommend this shirt.