Just purchased one of these to layer under a snug and light winter sports jacket. It is just perfect. Almost no bulk, so the jacket is not stretched at the vents, but a very good, densely woven layer of insulation.
I had previously bought these for my nephews, but I'm now looking at one or two more for myself.
This is the third Fitness Fleece Quarter-Zip I've purchased from LLBean over the years and I love them all. The light-weight fabric is perfect for year-round wear, whether I layer it in winter, wear it over a turtleneck or polo in spring or fall, or keep it handy for a summer's chill. The fit was as advertised and it launders nicely.