M3 threaded hole is more convenient to install, not easy to slip, save installation time. (Except some countries and APO/FPO). Service transit time is provided by the carrier and excludes weekends and holidays. Transit times may vary, particularly during the holiday.We care about our valued buyers, if you have any questions, our customer service staffs will be very glad to help you. We try our best to reply to your emails as soon as possible, however, due to high volume of daily incoming emails. And time zone difference, we may not be able to reply your emails immediately. Feedback is very important to us.