Ventz ® is a patented & European venting system designed to funnel cool air into your jacket.

When riding in warm weather the air locked inside your jacket creates an invisible blanket of trapped air that raises your body temperature to uncomfortable levels. Ventz ® creates a regular flow of soothing air that strips away this heated layer making your journey more comfortable and your arrival a lot cooler. Works better on some jackets than others, but I found them quite useful. I finally went to a full mesh riding suit so these are a bit redundant for me now.
You can click the video link in the weblink for a short video of these working.