A fluid filter arrangement includes a housing defining a slot arrangement. The method consists, in essence, of grouping sensed pixels by geometric blocks over the inspected surface and comparing each block with a corresponding one from another die on the same wafer, from another wafer or from a stored model image. An example of a secondary elastic seal could be O-rings. The chamfer portion includes a first leg disposed upstanding relative to the base portion, and a second leg portion angularly disposed relative the first leg.