Products may not be returned for credit except with Merck's permission, and then only in strict compliance with Merck's return shipment instructions. Distributor must obtain advance written authorization from Merck and a written return authorization document in the form then in use by Merck, prior to returning any Products. Certain items and quantities may not be returned for credit or under any circumstances. These items include, but are not limited to: diagnostic reagents, refrigerated or frozen products; reagents and standards which have passed their expiration dates; custom products, special orders or modified products; products missing labels, parts, or instruction manual; and books, computer software and equipment removed from their original containers with the original labels affixed and unaltered in form and content. Where applicable, the Distributor agrees to provide Merck with interim product temperature and other appropriate storage documentation and to package Products with proper refrigerant to maintain required temperatures during transit. Any returned items may be subject to a processing fee and restocking charge. In no event will returns be authorized after ninety (90) days following shipment to Distributor.