These blades are "formed", which creates the right amount of suction under the deck to create enough turbulence to effectively "chop and drop". Since the blade does not have aerodynamic fins, there is very little discharge, less noise, and vibration, and due to the shape of the blade, less drag as the mower propels. Sharpening this blade is overrated in my opinion, it's tough, keeps the sharp edge longer and self sharpens. This is the blade that came on the original "Kee Trailmate", which at the time was made by Manco, a go-cart manufacturer. I was told by the Gravely dealer that it was "not available", did some research and discovered that Ariens and Gravely, which continued manufacturing the mower after Kee was sued, discontinued the blade and replaced it with a traditional vacuum blade, which was designed for baggers, of course the Trailmate doesn't have a bagging system (the first version, Manco made, actually did have a bagger however) when Manco removed the bagger due to weight and stability issues, they designed this blade.
