Bicycling.com : "Unlike many headsets that just have a single seal on the bearing or race, the 40 Series has both, doubling the protection.
CANE CREEK 40 INSTALL ON MONGOOSE XR PRO BIG BOX BIKE BUDGET BUILD
The seals don’t add any noticeable friction, allowing your bar to turn smooth and free."
Competitive Cyclist: "With Cane Creek's 40-Series Headset, you don't have to worry that spending less will equate to getting less performance. It's the working class headset that offers serious durability and smooth performance, rivaling their 110-Series Headset."
Bike Rumor: "When it arrived, I was impressed by the look of Cane Creek’s newest headset. The Forty-Series (and it really is a series, with dozens- if not hundreds- of variations)"...
Singletracks.com: "There are a few refinements to the design, such as a different top cap that holds the upper seal while securing the compression ring."