Giant bikes and there d shaped seat post.

[Chap sur le velo]

I have a defy pro and love it.
Recently cycled behind a weighty cyclist on a Giant and I was surprised that at times I could see their seat stem flexing. It was on a section where I was working too hard in and out of the saddle to be able to determine if mine was too, but I assume so.

That said the rubber cap is poorly designed and doesn't stay in place long.