A very popular jacket made more versatile by removable sleeves. Providing total wind block with good wearer comfort, this fabric is a favourite of ours; it is soft and quiet, feels good next to the skin and is easy to care for. It was difficult to believe that a jacket as light as this could provide such a high level of weather protection, it is an amazing piece, perfect for running. Offering year round versatility simply layer over a good base, thermals in winter over a bra or tank to beat spring and summer wind chill.A medium equates to a size 12.