The HG L2 freehub is the cutting edge of premium road technology and was launched with the latest generation 12-speed DURA-ACE 9200 groupset. It was specifically engineered to allow new DURA-ACE 12-speed cassettes to be made from aluminum instead of titanium, while still maintaining positive engagement between cassette and freehub.
Aluminum is lighter and more cost efficient than titanium when it comes to freehubs, but it’s also easier to damage. Before the HG L2 design, aluminum freehubs would quickly show signs of pitting due to the high pressure and small surface area where the cog contacts the freehub. The HG L2 design eliminates this issue by using smaller, deeper splines on both the freehub body and cassette cogs, which disperses these forces while capturing the benefits of aluminum.