All cores must be received at the time of purchase or a core charge will be added to the invoice. Diesel Injection Service reserves the right to inspect all cores for damage prior to credit being issued and also reserves the right to reject all damaged cores. All core must be returned to Diesel Injection Service for core credit within 30 days of purchase for full refund. After 30 days, a 20% restocking fee will be assessed and an equal fee will be assessed for each additional 30 day period thereafter. There will be no core credits issued after 6 months.