Product details:

Surly's Stainless Steel Chainrings last longer than their aluminum brethern because the 304 grade metal they use is 35% stronger. The rings aren't pinned or ramped so when one side starts to wear you can flip it around and pedal some more They work great with singlespeed, fixed, and 1x9 applications, and the teeth are 2.1mm thick so they work well with 9-speed chains.