This is THE bun used by over 90% of Chicago hot dog stands! Baked by Chicago's own S. Rosen's, a tradition since 1909. Kosher Parve. PLANNING A PARTY? Please note we ship on Mondays only. Orders must be placed by midnight (central time zone) on Thursday to be shipped the following Monday. These buns arrive freshly baked. Consume by expiration date or freeze prior to that date for up to four months. For optimal freshness, thaw at room temperature before serving.