@Giles:

It is the least breathable denim we do.  It makes 25oz feel like wearing a string vest in comparison….

Hahaha I was afraid you would say that. Thanks for the help Giles!

I apologize in advanced if this is a silly question, but I was wondering, how well does the fabric on these breathe? I have a pair of the 634S in the flagship 21oz and I feel like those breathe fairly well making them a nice year round pair. Whereas my 25oz feel like a damn sauna the moment I start doing anything "active" in them. Just wanted to see which one they're more comparable to.