This IS the go to long sleeve crew neck.   Hard to find but made by Copper Key, it wears like a second skin.  So thin you can layer several at once or fold it up and put in your purse for a quick warm up.  It is perfect to pull out when the wind starts to pick up on those cooler evenings at the beach when your skin needs a soothing after too much sun, or even as PJ tops, they just feel good!