These boots are extremely light weight and not at all bulky.  They literally weigh about as much as my running shoes. They are also very comfortable and reasonably warm to wear in winter in NYC.  The only tradeoff for them being so light is that the sole is not very thick -- it's even thinner than an average sneaker ... feeling is somewhere between a sneaker and a slipper. I do hope they last.  I wear these boots for scooting around the city when I want to save my feet from marching all over Manhattan in dressy boots.

As for sizing, I have medium-sized/athletic calves and would say these boots zip up around my legs just a bit more loosely than most other boots I have.  They're not so loose that they gape, but I can easily tuck pants in. Still, they're snug enough for just wearing tights/leggings. The insole is a tad wider than most boots (comfy for me, not too wide), and I think the insole length is just a hair shorter than usual but not a problem for me.  Basically I ordered my usual size and they fit very nicely, though my big toe does feel closer to the front than it usually is.  Would have given a full 5-star rating, except that I do wish the sole was thicker and offered more support/cushioning.  But they're comfy as is, and I like them.