This specification covers concrete drain tile with internal diameters from 100 mm (4 in.) to 900 mm (36 in.) that is intended to be used for surface and subsurface drainage. This specification is applicable for orders in either SI units (M 178M) or in inch-pound units (M 178). SI units and inch-pound units are not necessarily equivalent. Inch-pound units are shown in brackets in the text for clarity@ but they are the applicable values when the material is ordered to M 178. Note 1??This specification is a manufacturing and purchase specification only and does not include requirements for bedding@ backfill@ or the relationship between field load condition and the strength classification of drain tile. However@ experience has shown that the successful performance of the product depends upon the proper selection of the class of drain tile@ type of bedding and backfill@ and care that the installation conforms to the construction specifications. The owner of the reinforced concrete pipe specified herein is cautioned that the field requirements must be correlated with the class of pipe specified and provide inspection at the construction site.