Pick the wrong size, and you pay for it twice. Once at the packing table, when you wrestle a shirt into a mailer two sizes too small, and again at the carrier counter when your package bumps into a higher postage tier because it bulges past the allowed dimensions. Getting the best poly bubble mailer size for each product type is one of the fastest, lowest-effort ways to tighten your margins as an Etsy or Shopify seller.




