The Micro Zip Tee is a damn near perfect piece that fits into the modern layering model of outdoor clothing. As a mid-layer it is light & breathable with enough insulation for active winter pursuits & will provide good insulation with minimal bulk. Alternatively it works brilliantly as an everyday cosy jumper. The Polartec Classic Micro 100M is the lightest weight fleece fabric that Polartec manufacture & is proven to last longer & is more durable than the “run of the mill” fleece. Flatlocked seams reduce bulk & improve next-to-skin comfort & just like most synthetics it wicks moisture incredibly well & dries pretty fast too. Polartec Classic Micro 100M Light, warm & quick drying Flatlocked seams for enhanced next-to-skin comfort YKK cantre front zip For the kit geeks, below are links to M.E.s Technologies Page that has a bit more info on fabrics & construction. Polartec Classic Micro