Wool overshirts became the foundation for many early "uniforms" simply because they were already the common everyday men's workwear of 1861.  A plain wool overshirt not only is great for To the Step, but will work as a spare warm shirt for any impression, U.S. or C.S., at any point in the war.  Our Group Buy overshirts will be made from either grey or red wool by Honest Sutler, and will be copied from a surviving original shirt.  They will be made in a size regular (will fit up to a 42 chest) or large (will fit up to a 48 chest).