Using Priority Mail Flat Rate boxes and envelopes can help save you and your buyers money in shipping costs on heavier LEGO parts orders (packages that weigh above 13 ounces). Flat Rate boxes and envelopes are great because the boxes and envelopes are FREE and you pay a reasonably priced flat rate for the shipment regardless of the weight (up to 70 lbs within the United States). As an added bonus, you don’t even need bust out your postal scale (sweet!).
So how do you get your hands on free USPS Flat Rate Boxes and Padded Envelopes? You can pick Small Flat Rate Box easily by visiting your local post office or by ordering them on USPS.com (free shipping). Padded Flat Rate Envelopes, on the other hand, are NOT kept in stock at the post office. You must order them on USPS.com (free shipping).
In terms of volume, the Flat Rate Padded Envelope serves as a fantastic shipping option with a much higher volume capacity than Small Flat Rate Boxes for roughly the same postage price. Yes, you can stuff flat rate envelopes full. Just make sure your LEGO items are still packed safely and securely and you can still seal the envelope.
USPS Priority Mail 2-Day Small Flat Rate Box
Dimensions: 8-5/8″ x 5-3/8″ x 1-5/8″
Rate at the Post Office: $5.95 (Online Price: $5.25)
Available at Post Office: Yes
Available Online: Yes (order Small Flat Rate Boxes free on USPS.com)
USPS Priority Mail 2-Day Flat Rate Padded Envelope
Dimensions: 12-1/2″ x 9-1/2″
Rate at the Post Office: $6.10 (Online Price: $5.70)
Available at Post Office: No (must order free on USPS.com)
Available Online: Yes (order Flat Rate Padded Envelopes free on USPS.com)