- This medium-weight Modal fabric (Birch tree fiber) sweat pant is perfect for any clime & will be your favorite yoga pant, ever! Perfect 4 Yoga, lounging & running errands. Bamboo green stitch details. Flex waist band with luxe draw cord. 2x1 RIB piping from side of pant to top of rear provides amazing stability & flexibility during rigorous activity. Easy to taper length.