Description of Arcteryx Rho AR Top The dual identity of these wicking layers makes the Rho AR Top great both as a warm expedition foundation or as an ideal aerobic midlayer. Wicking and mobile Polartec® Power Stretch® fabric provides a comfortable and solid foundation, and superior stretch won't impede intense athletic movements. The ideal Arcteryx midlayer for aerobic activities. Features: Polartec Power Stretch Collar zip Form fitting Great warmth-to-weight ratio Laminated pockets with zips