No contaminants of any kind including, but not limited to, non-diesel fuels, gasoline, any substance that causes rust, stains, corrosion, or foreign debris. No signs of modification, tampering, abuse, or non-original parts. No signs of performance related damage this includes, burnt tips/altered parts. Must not be due to improper application, installation, or operation. Return the unit in a well protected box with materials such as bubble wrap, crumbled paper, cardboard, etc. Any units sent without proper documents/information, risk being identified as a core and, once identified as such, the decision will not be reversed. We reserve the right to alter or modify this policy at any time. We only want to offer the best service possible for you.