Here is a template for the MS-508 rectangular labels. Due to the small label size, 5/16″ X 1/2″, not much can fit on each label.
Before printing, and wasting sheets of MS-508 labels, cut out plain paper sheets of the same size.
Beware, printers have non-printing areas. Some printers non-printing areas are bigger than others. Depending on your printer, and there are many many printers out there in the wild, you could be able to print all the way out to the edge of the page. Or, you may not be able to print, or partly print on the top row, bottom row, left column or right column of labels.
The Text Direction was changed to Vertical because you can just fit more text. Depending on your printer, you might have to do some fiddling with the cell margins to get things to print exactly on label on your particular printer.