2 different print size printers hooked up to the same computer

I have a thermal printer (for 4 X 6 labels) and an inkjet printer (for 8.5 X 11 labels) both hooked up to the same iMac.

Is there a way to have 4 X 6 automatically be printed when I select the Thermal printer, and 8.5 X 11 paper be printed when I select the inkjet printer. I own an e-commerce company, and we need to print a 4 X 6 shipping label, and a 8.5 X 11 packing slip with every order. It is so tedious to go in to Page Setup and change the page size every time.  Thank you in advance.