Hi Vis Fleece Tops are made from 100% polyester, the weight of material is a good guide for how thick (and how warm) the top is. As a rough guide 200 to 300 gsm fleece would be better for warmer climates. 300 to 400gsm fleece is a thicker weight and great in the cold. The Syzmik ZT460 / ZT461 are good examples of a “heavyweight” fleece top.
On this web site we use the term Fleece or Polar Fleece to indicate the material is “fluffy” and the term windcheater to indicate the material has a smooth outer finish. (It can be confusing since some manufacturers refer to the windcheaters as fleecy)