By the Book

You can use the Dymo 30256 shipping size label.  This label is 4" x 2 5/16".  It's a great size because the name can print out much larger and you can print your logo on it.  The rolls of 30256 come 300 labels per roll.

The other size supported by Roll Call is the Dymo 30334 Misc size.  The label is 2 1/4" X 1 1/4".  The rolls of 30334 come 1000 per roll.

These are the ONLY sizes supported by Roll Call.