First what does "ttt" mean?
Now on to your question: Besttop make a Windjammer which appears to be similar. The Rock thingy you're interested in is supposed to "seal out" dirt and other things but from the photo it looks to be somewhat loose and doesnot seal up against the roll bar. I think my Windjammer was $70 so there's a huge difference in cost. I'm happy with the WJ but then I don't have AC and it doesn't rain here in the desert.