the advantages of a parcel over flats or letters are:
1. You are paying only about half, if you print your own postage: $2.66 v (?) with flats.
2. the parcels come with free tracking bar codes. (EBay requires tracking bar codes, I think. Whatever the cost, tracking gives you peace of mind).
3. Easy to click to generate PARCEL shipping label on PayPal transaction. Not so or impossible with letters and flats via PayPal..
4.generally need that extra thickness of PARCELS to protect chips of any decent value.