Order # for USPS envelopes

[RDH79]

Does anyone know the item # for the fiber type envelopes the postal service has? Not sure if they are Flat rate or Priority. I have searched there site but they dont say what there are made of.
Thanks
Rich

 

[Russianwolf]

the priority flat rates are thin card board/card stock.

The fiber (silk like material) are Tyvek I think.

 

[RDH79]

Thanks Mike. I seen tyvek and Googles it. I think thats it.

Thanks
RichH.

 

[Monty]

Is this the one you want?
https://shop.usps.com/webapp/wcs/st...viewAll=Y&rn=CategoriesDisplay&WT.ac=10000273