When I order from a site that I'm not so sure about, I always check to see if they take paypal. This way no credit card numbers go to the site, and paypal backs you if the product is shady or you never get it. This site does take paypal.
As for the quality of the rulers, I'd email them and ask about the thickness of the rulers. This covers you in 2 ways..one..you'll know how they behave as a company with customer service, but more importantly, you'll have locked them in, in writing about the thickness and material of the ruler.