Adding Thumb Size to product images

Hi,

I've setup MarketPress here, however the thumb size isn't the same. I have incorporated the CSS from Framemarket theme, since it is going into an existing site. How can I make the thumbs resize to be the same on all products? Here are two examples of products:

http://fcnyc.glocalwebtech.com/store/products/200-food-test/
http://fcnyc.glocalwebtech.com/store/products/paleofiber-unflavored-powder-drink-mix/

Thanks!

Dana