Fastenal stocks many of the fasteners at our plant and routinely puts the wrong parts in our bins. Today it was the remnants of 6-32X5/8 screws buried under a pile of 8-32X5/8 screws. Several of our bins are marked to warn us that a bin contains parts that are slightly over- or under-size. Our buyer tells me that our Fastenal contact refuses to acknowledge there is a problem and basically thinks he is our sole source and doesnt need customer service skills.