| Owner: | Union Pacific Railroad Company |
| Type: | Flat Car |
| AAR Class: | FMS: Specialty Ordinary flat car for general service. This car has flooring laid over sills and without sides or ends. |
| AAR Type: | F421 |
| Detail Info: | Flat Car, Load Limit: 200,000lb and greater, Equipped with cushioned draft gear/underframe, Inside length: less than 53ft |
| Plate: | B |
| Max Gross Weight: | 526000 |
| Load Limit: | 464800 |
| Ext L/W/H: | 64' 8" / 10' 0" / 8' 0" |
| Int L/W/H: | 44' 4" / 10' 0" / 0' 0" |
| User Notes: | Space Shuttle Rocket Booster |
