Convenience and economy are primary reasons why contractors order concrete from ready mix suppliers. Besides mixing and delivering concrete, ready mix trucks usually can place concrete by chute directly into forms. But to ensure high-quality ready mixed concrete, contractors must order the mix carefully, make sure the trucks meet industry standards, and, if possible, use the trucks for placing concrete. Contractors can order concrete mixes that provide the fresh concrete properties for workability and finishability, yet yield excellent long-term performance. But to obtain these advantages, they must provide the ready mix producer with adequate information. ASTM C 94 "Standard Specification for Ready-mixed Concrete" provides general guidance on specifying concrete. The contractor must provide the ready mix producer with the coarse aggregate size and the slump and air content needed when the concrete is discharged from the truck.