Martha Ward writes:

I am looking for an insert for "Timms" cassettes.  The ones we have are
>12 years old and we are down to the last 4.  We use them to freeze our
skin punch bxs. as well as renals in liquid nitrogen.  They are white, 1
inch square, and the circle is 3/8 inch in diameter.  I am hoping that
someone out there can help me find these.  I looked in every catalog we
had with no success.  Thanks in advance!