Here's what other sites are saying:
The Essential Run 1/2 Zip top from Brooks works hard to keep you comfortable on cool days, and it excels under a shell during cold weather. Moisture-wicking, quick-drying polyester offers soft stretch, top-notch performance and high mobility. 9 in. front zipper offers ventilation, and a stormflap shuts out chilling drafts. Thumb holes hold sleeves in place when arms are in motion and keep wrists warm. Zippered side pocket works with your music-player earphones. The semifitted Brooks Essential Run 1/2 Zip top is not too tight and not too loose.