7 Pa. Code § 59a.337
Bulk bins must be constructed of stainless steel, aluminum or other equally corrosion-resistant materials, free from cracks and seams and have an interior surface that is relatively smooth and easily cleanable. Product contact surfaces must be easily accessible for cleaning. Portable bins must comply with the current 3-A Sanitary Standards for Portable Bins for Dry Milk and Dry Milk Products.
This section cited in 7 Pa. Code § 59a.326 (relating to equipment and utensils).