I have emailed them and the response was as follows.
"
Alan K Martin (Order a Print)
Dec 1, 09:46 IST
Hello Aymar,
Thank you for using our service and reaching out to us!
The system does 3 things:
First, it shows the sizes that are the closest to the photo ratio.
Second, it presents the sizes that can be printed using photo quality.
Third, it presents only the sizes that are available in your customer's country.
The system will always prefer to offer sizes that have an aspect ratio that is the closest possible to the aspect ratio of the original image in order to prevent image data loss.
In order to get the best results and to enable printing of most products/sizes, the artwork should be uploaded in the size of 4000 px or higher in sRGB format, 300 dpi or more, so we can print as close as possible to what the customer sees on their screen, using JPG or PNG file type.
Unfortunately, we cannot send free samples, but we offer our clients a sample request discount that takes 20% off from the total price from the first order. You should see the discount in the cart before checkout. (If you are logged in as the site owner)
We are using the most advanced printing equipment and materials to achieve great print qualities.
The paper stock depends on your customer location as we ship from local factories, but in most cases, we use Art Poly canvas, Kodak ENDURA professional photo paper with a fine grain pebble texture and Glossy âFâ Kodak ENDURA professional photo paper with a glossy finish and many other great materials.
If you have any further questions please don't hesitate to contact me.
With best regards,
Alan K Martin
Order a Print - Support Team"