Got through to USPS (800-610-8734)

The representative I spoke to was well aware of the free "ground advantage" boxes and mailers. All the following come in packs of 25. I was able to order 75 of each box and 100 of the mailers. If you need more, you can, that's just how much I wanted to start off with.

Box 1: 12 x 12 x 8.5

Box 2: 14 x 7 x 5

Poly Padded Bubble Bag: 12.5 x 9.5

Paper Padded: 14.5 x 20,5

Polybag: 14 x 17

I was told it would take 7-10 days to arrive.

Of course, they will ask you for your Poshmark closet name. Hope this helps! I was hung up on about 10 times, and finally on hold for about 30 minutes, and had a very helpful and pleasant representative.

And according to the following link on usps website, ground advantage is eligible for free pickup

https://faq.usps.com/s/article/What-is-Package-Pickup#eligibility