Single product page image size?

I use woocommerce with Optimole. Optimole serves the images depending on the screen size. Optimole picks the right image size for the visitor’s browser and viewport.

But I am having the issue on the single product page. Optimole is not serving the right size for the screen.

Optimole says
“because you have fixed width and height defined for the <img elements and they are always the same 600px and 1000px no matter the screen size.”

How can I make this work?