USPS Flat Rate dimensions missing initially

I lied above. Not an Automation rule. It’s a Mapping.

And here’s another that just came in: Express is mapped to USPS Priority Express/Flat Rate Padded Envelope.

Hey JeffVan, 

I looked over your shipment activity 

10/14/2026 17:43 by: Shipstation

Marketplace Mapping (USPS Priority. Weight limit applies. 3-5 bus days.) Applied: Provider: DHL Express, Service: USPS Priority Mail, Package: Small Flat Rate Box.

10/14/2026 17:43 by: Shipstation

Product Mapping Applied Provider: Stamps.com, Service: USPS Priority Mail, Package: Small Flat Rate Box.

10/14/2026 17:43 by: Shipstation

The weight was automatically set to 19.80 based on the product defaults setup in ShipStation

From what I can see it seems that may actually be product defaults. I do wonder if you can set up an automation to set the dims, if they are always similar. Do find it odd it adjusts itself after you refresh the package type though. 

I don’t save product defaults very often because the defaults aren’t saved for each possible combination of Service/Package, and they are nearly always different, making it a fairly useless feature.

Here are the settings for this product:

I don’t know how to determine from this screen if these are saved settings.

Until very recently, the dimensions USED to default to 0/0/0. ShipStation added the dimensions recently for flat rate shipments, and I had never set them in a Rule because I assumed (maybe correct, maybe not) that dims were ignored for flat rate shipments, esp. those for which USPS already knows them, like SFRB. Now that USPS has enforced dimension requirements, ShipStation is furnishing them where they are known, which is great. Sure looks to me like SS knows the correct dimensions for a SFRB...they are just not filling them correctly until I re-select the package type.

Hey JeffVan, 

Good callout, I’ll talk to some people on the L3 team to see if this should be escalated or not. I have a feeling it will be, but I want to make sure that’s the case. I have a feeling this is happening because of the recent changes to the requirements like you said. 

Juan, please see my PM and the email I sent you with SharePoint links to the videos you requested.

Hey JeffVan, 

I did see those videos and sent them to the correct team, I’ll respond once they tell me what is causing it or if they release a fix! 

Thanks for letting me know. I’ll look into the JIRA and see if it was closed out.