I'd say they are doing enough volume to have their own blanks custom made to their specs as opposed to just buying from a domestic supplier or distributor. But they look like a fashion fit 100% ringspun combed cotton tee. Check out some premium blank suppliers like American Apparel, Alternative Apparel, JS Apparel, Royal Apparel, Article1, etc. It may not be exactly the same, but you should find some good options that are pretty close.