"J. Mc Laughlin" wrote in
:

Dear Ian (also my father's name): Thank you for your note. It is a
mystery to me why those who sell via the Internet do not work hard at
keeping their sites up-to-date. 73, Mac N8TT

Mac, If you have your heart set on #31 mix, this option isn't a good
one... but if you can use #73 or #43, you will regularly see sleeves in
various sizes and materials on Ebay. Many have Fair-rite numbers so you
can check to see if they suit.

Some advertisers state that the cores are Fair-rite cores, if they know
that, they should know the part numbers though they don't always state
them in the descriptions.

I have bought ferrites from one of the suppliers, the goods seem to
comply with the part number descriptions (dimensions, mu) and their
service to Australia was quick and cheap.

In this part of the world, product from Asia is available economically...
but we have to characterise them and long term product availability is a
bit of an issue.

Owen