Presorted Standard 500 pieces are required to qualify for Presort Standard. Post office delivery time is estimated at two weeks. Cheapest postage rate but the longest delivery time. Presorted First Class 500 pieces minimum Post office delivery time is estimated at 1 - 4 business days. Non-Profit (Standard) 500 pieces minimum Provide proper documentation to qualify for Non-Profit rate. Read: PS Form 3623 Post office delivery time is estimated at two weeks (Same as Presort Standard). Uses customer's Non-Profit account with 4OVER4.COM’S permit number. https://www.4over4.com/printing/category/direct-mail-services