Surface structure; contamination by self containded ingredients (poor distribution) i.e. unopened fibres
Acceptable if: friction side <=2% of area, non-friction side <=4%.
Higher porosity material
Acceptable if <5% of surface area; provided it is evenly distributed. High porosity area must not be through thickness of the disc.
Gasing split (Disc edges) bore or outside diameter
Acceptable 5 mm long on a 200 mm dia disc and 10mm long above 200mm 0,5mm open and 5mm deep; no more than 2 allowed.