Ultra Heavy Flannel Vintage Check Work Overshirt - Green IHSH-428-GRNIHSH 428 GRN To a great extent, the ultra heavy flannel (UHF) shirts define Iron Heart: heavy, rugged, but amazingly wearable. The 12oz fabric is woven with Aspero cotton from the foothills of the Andes mountains. Iron Heart double brushes them on the inside and single brush them on the outside, resulting in a very soft yet substantial, thick, warm and windproof flannel. Designed as an overshirt, this cut is an ideal winter layering piece, worn either