Emission devices vary according to their flow rate, hydraulic characteristics and wetting pattern.  The ideal emission device is durable (withstands outdoor conditions), resists clogging (large internal passageways, self-flushing), is insensitive to pressure variation that occurs as a result of slope and/or lengths of run (pressure compensating), accurate (low manufacturing Coefficient of Variation, or CV), and is economically affordable.  Drip irrigation emission devices are typically installed on the surface such that there is flexibility in placement and convenience for management.  These attributes are achieved via advanced plastics, hydraulics, and injection molding technology. Drip Tape Drip Tape is a “line-source” product that incorporates a series of relatively inexpensive, engineered emission devices into a thin walled tube.  Water is distributed evenly along the length of the tube through emission devices which may be spaced anywhere from 4″ to 24″ apart.  To accommodate various crops and terrain, tube wall thicknesses are available from .004″