Description of Marmot Reactor Half Zip The Reactor Half Zip is a clean, effective 100-weight micro-fleece sweater that takes the nip out of chill weather or low thermostats. Features: Weight: 10 ozs / 284 g Shell material: Polartec® Thermal Pro® P-460 Half-zip pullover style Flat lock construction Designed to fit over a light layer Polartec® Classic 100 Micro