I have no idea but there are a couple of threads on here where a lot of people are using flower nails instead. You grease and flour the nail as you would the pan then put it in with the flat part down and pour your batter. When the cake is done and you flip it over you just pull the nail out and it apparently leaves a smaller hole than a heating core. Hope this helps
Here is a link with all that info.
HTH
http://www.wilton.com/store/site/product.cfm?id=3E30ACBE-475A-BAC0-505CDCE7A4EA25E5&fid=5A8F6789-475A-BAC0-577BD7D8FE9B012D
a heating core reminds me of an individual, aluminum popover pan. a taperered flat ended cone.
you place it in the center of your cake pan(the larger ones and large 3d pans)...make sure to use shortening and flour, non stick spray or something on it before placing it in there and filling your pan.
you can get them from michael's, ben franklin, wilton, bakery equipment suppliers.
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