List the sizes you have to exchange and the size you are now. You never know there may be someone closer to you than you think. The ONLY thing that I ask is DO NOT post your address in the thread. Send a private message to the person you would like to exchange with. If you do not know how to do that, click on the person's name on their avatar, one their profile comes up to the right toward the middle of the page it will say send a private message click that. If it is a newer person that doesn't have contact information, they will have to message you, so if that happens just ask in the thread for them to send you a message and it will work.
The post office has the boxes that are one price so you could put a lot in those boxes. The shipping fee would probably or will be cheaper than buying ONE new shirt when you can get several.
If anyone has any questions just ask or send me a message, y'all know me I will help if I can

Happy Shopping!!!
