Grado Wood Body Retip Exchange Procedure 1). After placing an order for a Grado retip from the Needle Doctor's online store, a return authorization number will be generated and emailed to you in the following business days. 2). Needle Doctor will immediately process and ship you a new Grado cartridge before receiving your used cartridge. 3). Please ship your old cartridge in the packaging you receive your new cartridge in. This will ensure quality packaging avoiding shipping damage. 4). Send your used cartridge to: Needle Doctor 6006 Excelsior Blvd. St. Louis Park, MN 55416 Please write your return authorization number (RA#) on the outside of the box. 5). You will be given a two week grace period for sending your old cartridge back to us, or the difference will be billed to your credit card.