That's the stock. Same basic idea as the ordinary 550 FS, but with different pattern checkering, different cheek piece, longer grip cap, and I believe perhaps a more acute grip piece radius. I'm holding off getting the 6.5x55 until I can get one with this stock. I believe that it has been offered in other calibers, but I also believe it has been available in the 6.5x55. We'll see.