This can be caused by a lack of material availability, a change in vendor, or to compensate for a design error. An ECN must contain at least this information: Identification of what needs to be changed. One of the most common ECOs in ASIC design is the gate-level netlist ECO. In this flow, engineers manually (and often tediously) hand-edit the gate-level netlist, instead of re-running logic synthesis. This should include the part number and name of the component and reference to the drawings that show the component in detail or assembly.