Reduces chill factor
This is the first base layer article of clothing I have purchased so I don't have anything to compare it to. First, the sizing is slim. I'm a big guy and have to squeeze in and out of it. I knew it would be tight so I can't complain. The front has a form of plastic imbedded in it so it cuts the wind reasonable well. The cold still gets around to the back of my arms but it protects my torso which is what I really care about. The back is mesh so it breathes sufficiently. It's basically a backless windbreaker that you can wear under your jersey. Overall, it works but I don't recommend it for colder than 45 degrees or so.