The difference is in the construction!
Round rings are mounted on the spine, making repeated opening and closing a burden on the binder and its contents
The curved shape of the D-ring means there's less wear and tear on your pages and your binder because you're not moving the paper every time you open the binder
Acid-free poly material will not stick to materials stored inside
Environmentally friendly: does not contain PVC which produces chlorine gas when incinerated
Archival safe for all documents including photos
Superior cold-crack resistance, down to 0° Fahrenheit
Front and back inside pockets for loose sheets