Warning everyone that once you try these merino jerseys, you probably won't go back to anything else. I ride with these long sleeves from fall all the way to mid-spring. If it's cold, it provides with enough warmth, if you sweat, it dries super quick, if your sweat tends to stink with other materials...well, you don't stink! You can wear it several times wich also makes it great for multi-day adventures.
For the bikepark, I would choose another material, more resistant to potential crashes, like the Mission jersey. For anything else (I use them even for backcountry skiing and hiking), these merino jerseys are exactly what you need. I guess that's why they get sold out so quickly!