I've had an eBay order arrive via Fedex in a flat rate box. I doubt anyone at Fedex cares as long as the label scans. I've also seen USPS labels printed on the

I've had an eBay order arrive via Fedex in a flat rate box. I doubt anyone at Fedex cares as long as the label scans. I've also seen USPS labels printed on the free "UPS USE ONLY" thermal labels.