Is the postage needed for mailing your 5.25" disks costing you more
than the disks do?  Perhaps I can help.  I have found a source of
better mailers.  They will ship a disk & cover letter for two ounces.

Williamsburg Box & Partition Co, 234 N Front St, Williamsburg OH
45176-1397   Call them at 800/927-2972, and ask for Dorothy Lewis in
customer service.  Please tell her that Dave Byter sent you, so that
I get my finder's fee.  She will send you a sample of the 6 by 8
kraft (generic brown) flat mailer.

When you get your sample, put your old Calumet mailer and a disk on
your postage scale and weep.  Then put the Williamsburg mailer and the
disk on the scale and rejoice.  And now, for the consumate act, put on
another disk, and throw your old mailers into the trash.

Presently (Mar 91), the minimum order is 300 mailers (2 cases).  In
the 300 mailer lot, they cost $0.171 each.  Plus 25 pounds freight.
Larger lot = smaller price, down to $0.114 if you need many thousands.