1.1 This specification covers wet-cast precast modular retaining wall units cast from first-purpose concrete with or without the inclusion of steel reinforcement. The precast units covered by this specification are machine-placed units intended for use in the construction of dry stacked modular retaining wall systems. 1.2 The text of this standard references notes and footnotes that provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard. 1.3 Units—The values stated in either inch-pound units or SI units are to be regarded separately as standard. Within the text of the specification, the SI units are shown in brackets. The values stated in each system are not exact equivalents. Therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.