Size is off

Not happy with my latest order. I had ordered a size L t-shirt a couple of years ago from StickerMule, and it fit perfectly. I ordered a new L shirt this time around, and it's huge compared to the first one. It's more like an XL. Not only that, but the fabric feels thinner. I'm going to wash/dry it and see if it shrinks, but I doubt it's going to shrink enough to reach the same size as the first shirt I ordered. Customer service was very good when I contacted them since the shirt got lost in the mail, and they had to send another one.