2-part internet postage labels with recipient address and postage indicial label on one form. For use with Stamps.com, Endicia and other PC Postage services. Labels work with any envelope, flat or package Postage and recipient address print on separate labels. Not for use with window envelopes or pre-printed bill pay envelopes. And cannot be used for Priority Mail because the return address is not printed on any label. Compatible with DYMO EL60 and Turbo printers. When printing labels for use on envelopes (sizes 9-12, Personal, Monarch and Custom Sized) , the USPS requires that you use the fluorescent labels supported by Stamps.com. When printing labels for use on larger envelopes and packages, you are not required to use fluorescent labels. DYMO (R) LabelWriter (R) 30384 Fluorescent Internet Postage Labels, 2-Part, For First Class And Express Mail is one of many Address Labels available through Office Depot. Made by Dymo.