G'day Matt, 

The compression sack is water-repellent, but not completely waterproof. Could be an idea to pop it in a dry bag as well if you need to keep the sleeping bag waterproof.

G'day Zach,

Yep, every Sea to Summit bag comes with the QuiltLok system - it won't be explicitly listed because it's a given.
You'll only find selective features such as ZipCoupling listed, as not all bags have that.
Hope that helps!

G'day Dave,

It comes with a compression stuff sack.
If you check out the second to last product image you'll be able to see this in action.
Just be mindful not to store your synthetic bag in a compressed state.

G'day Dan,

If you are 193cm, you're in the long size - no question.  The bag length takes into consideration the hood and the overall bulk of the bag, and not the internal dimensions, so you really need to abide by the max user height.
The Trailhead also has a flat foot box, not 3D, meaning there isnt a boxed space at the base of the bag for your feet.  This generally means the size of your feet will also chew up abit of the bags length, especially if they are big (which I assume they are based on your height).
Even if you were on the cusp of the max user height (183cm), I would recommend sizing up.  I say if you went with the regular you probably wouldn't get your shoulders covered.

No worries Dan, happy to have helped in your decision making!

G'day Jeffrey,

Sea to Summit recommends the medium stuff sack for the Trailhead Th2, however, the Regular length will just squeeze into the small as well if you wanted a longer narrower compressed bag.