One of the most familiar Pennsylvania Railroad freight cars of all time, the H21a was also the largest single hopper car class on the PRR. With over 39,000 cars built, the H21a had an amazing history of service and longevity with several hundred cars lasting well into the Penn Central era. During the 1940s and early 1950s, these hoppers were leased to both the Norfolk & Western and Virginian railroads. Atlas O's version is realistically duplicated from designs based upon actual historical documentation of the lease agreements.