Switching labels requires far more than just a single change to the height and with of the cells in a table. If you use Word's label tools, you'll see that there is a myriad of label formats to choose from for a given page size. Not only can the number of labels across and down the page vary according to the label format chosen, but so too can the vertical and horizontal space between the labels.

If both of the label formats you require use the same data, I'd suggest populating an Excel workbook with those data and setting up two label mailmerges - one for each label type.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]