My Mystere 5.0 XL has this. It's only about 2-3 inches across. I can't be sure if it's the T skeg but my 5.0XL always pointed better than the similar non-T 5.0. I seem to point better with speed than other skeg designs I race against, especailly in a long pinching beat to weather. It does a great job protecting the skeg from beach wear since the T acts as a wide solid glass sled. I'll get a photo today.