Expanding variant boxes on product pages all the way to margin

Site URL: https://www.andthenjewelry.com/collections/beni-shoga-n8amh

Hey everyone! 

for my site, I'm trying to make the variant boxes the same width as the text above them. is there a way to do that?

an example product page is; https://www.andthenjewelry.com/collections/beni-shoga-n8amh

thanks so much for the help!