Here's what's different:
Materials: the new S Filter is made of 100% surgical grade stainless steel (it's still made in the USA). Each filter is passivated with citric acid to remove any impurities before shipment. Citric acid is a natural alternative to conventional nitric acid, which is difficult to dispose of safely.
Design: the new S Filter uses two stainless steel rings to protect the mesh from both sides. The steel rings are tempered so they remember their shape, which improves durability and the whole design is slightly thinner, which makes it easier to screw into the AeroPress. Furthermore, with steel rings on both sides, there is no up or down side to the S Filter, so you can now insert the filter any side up!
Finally, the welds holding the filter together have been strengthened significantly as well. Based on our testing, weld separation is no longer possible under normal or even heavy usage - just don't run over your S Filter with a truck! :)
Here's what hasn't changed: the S Filter still comes with our lifetime guarantee. Your S Filter will never break. And if it does, we'll replace it for free!
To see videos of the new S Filter in action, head to: http://kaffeologie.com/guides