"... we purchased all of our ... 'Shroom Burgers from two suppliers, with approximately 50% of our 'Shroom Burgers supplied by each supplier ..." Shake Shack gets many of its products from a limited number of suppliers. Their 'Shroom Burgers, for example, come from just two suppliers, with each supplying approximately 50% of the product. So if something happened to either one of those suppliers, Shake Shack could run into serious supply shortages and higher costs. Source: Shake Shack