I have a lightweight jacket that has wind proofing in the front but vented in the back and the sleeves unzip to turn it into a vest. It helps to deal with the wind chill on a bicycle when it is cool and I can make adjustments as it gets warmer by first removing the sleeves and then the jacket vest. The sleeves fit in one of the pockets of my jersey and the jacket in another pocket or I could strap it to the handlebar.