Genuine Detroit Diesel oil pump gear. Detroit number, 5166821. Please be certain the part you are seeing is what you need. While our new old stock items are new and unused, some might not be in original boxes, or the boxes may show signs of shelf wear or soil. If you order multiples of our new old stock (NOS) items we will ship the cleanest boxes we have, If you reorder you may not get the same clean boxes but the part will be the same. We do not accept returns on (NOS) items. Please be sure you need this part which is identified by The OEM part number in the listing. It is your responsibility to ascertain the suitability of the part prior to purchase. We strive to give you the best possible service and will answer any questions asked on the ebay message system promptly. You may not get an answer on weekends or holidays until we reopen. While we will accept reasonable offers on our NOS items especially for a quantity sale, please do not expect to get a reply for ridiculous frivolous offers. We will not make a counteroffer for your offer. we will either accept it or decline. We invite inspection of any of our listed items in person prior to purchasing. We are open 8AM to 5 PM Monday through Friday.