I don't see it listed here. If it isn't, you have to make your own entry,
find an exact equivalent in another manufacturer's product range that is
listed, or see if the manufacturer provides a suitable template.

There may be something here..

http://www.pendaflex.com/enUS/CampaignsHome/Pendaflex__and_Oxford__Product__Temp
lates.html

To make your own entry...

In Word Tools|Mailings|Envelopes and Labels|Labels|Options (or in the Label
Options dialog in the MailMerge process, if that is what you are using),
a. select the correct printer type
b. click New labels
c. fill in the dimensions of your label stationery. The details are
sometimes
printed somewhere on the packaging or on a piece of paper included in
the pack. Otherwise, you will need to measure them yourself.
d. Give the label a name, such as Pendaflex 15, and click OK
e. in the "Label information" dropdown, select "Other/Custom" and your
label should be listed.