women's burton [ak] helium grid full-zip fleece. skin it, boot it, or just go for a hike. the women's burton [ak] helium grid full-zip fleece brings highly-breathable, midweight warmth to mountain missions of any sort. the pack-friendly design is wind and abrasion resistant on the front with an extra breathable panel on the back. it's a go-to layering piece that can stand alone on the hike up and works great under a shell in exposed alpine terrain or on the descent.