Yep, that's a blade that you got with the M5.5. I origanally acquired it for my M5.0 "bag-o'-extras". Allie Mims now has my old M5.0, you have the M5.5, and I now am collecting Nacra parts. For some weird reason I seem to have a stack of Hobie 20 rudders and boards. My garage justs sprouts extra stuff. Sails falling off shelves, boxes of blocks, etc; I need packrat therapy! Eight boats in ten years...like notches on a gun.