Complete Zip Files
-  Gerber file for each copper layer
-  Gerber file for each soldermask layer
-  Gerber file for each silkscreen layer
-  Excellon or Gerber drill file

Outer Layers:
-  Spacing
-  Trace width
-  Annular ring

Inner Signal Layers:
-  Spacing
-  Trace width
-  Annular ring
-  Inner clearance (drill to feature)

Inner Plane Layers
-  Spacing
-  Trace width
-  Annular ring
-  Inner clearance (drill to feature)
-  Thermal reduction

Drill
-  Double hits
-  Missing hits

Soldermask
-  Undersized clearances
-  Missing clearances

Silkscreen
-  Line width