According to LTT, the section containing the computer just weights under 190 grams (that's about the weight of an average medium-sized apple).

The battery is the counterweight.. which is actually a good thing to have.. I have a fist generation Quest and the main problem with that one was the weight distribution. Adding weight to the back actually made it more bearable. Just by looking at how thin the front part of this one is, I can tell this is gonna be so much more comfortable.