Printing on Index Cards using Pages.

Hello does anybody know how to set up Pages to print o index cards that are 12.58cm wide and 7.6cm high. My mac will not print it on this size of paper, it tries to print it on a regular 8.5 x 11 size? I have gone into the page settings in pages, manage custom sizes and made my size and click OK and it will not save the setting and print it??? I can load the paper into the printer side ways like you would an envelope but still nothing. thanks.