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| Name | Jurisdiction of Formation |
| Hourglass Acquisition I, LLC | Delaware |
| Preferred Rocks USS Inc. | Delaware |
| Hourglass Holdings, LLC | Delaware |
| USS Holdings, Inc. | Delaware |
| U.S. Silica Company | Delaware |
| Pennsylvania Glass Sand Corporation | Delaware |
| The Fulton Land and Timber Company | Pennsylvania |
| Ottawa Silica Company | Delaware |
| Ottawa Silica Company, Ltd. | Quebec, Canada |
| Coated Sand Solutions, LLC | Delaware |
| Cadre Services Inc. | Delaware |
| Cadre Material Products, LLC | Texas |
| Fairchild Silica, LLC | Delaware |
| Utica Silica, LLC | Delaware |
| Tyler Silica Company | Delaware |
| New Birmingham Resources, LLC | Texas |
| NBR Sand, LLC | Texas |
| NBR Maritime I, LLC | Texas |
| NBR Maritime II, LLC | Texas |
| Sandbox Enterprises, LLC | Texas |
| Oren Technologies, LLC | Texas |
| Sandbox Leasing, LLC | Texas |
| Sandbox Logistics, LLC | Texas |
| Sandbox Transportation, LLC | Texas |
| Mississippi Sand, LLC | Missouri |
| Arcadia Sand, LLC | Delaware |
| Boss Energy Resources, LLC | Delaware |
| Seagraves Development, LLC | Delaware |
| EP Minerals Holdings, Inc. | Delaware |