I'm looking at these aero bars and am a bit confused.

I saw a video posted in this thread and am quite interested in getting a pair. I at first thought I'd have to replace my current handle bars in order to get something like this but after seeing the pic at nashbar it seems that these things bolt on to existing handle bars, is this true, and if so would they bolt onto the handlebars on this bike, a Trek 7100.

They bolt to existing bars, and have some adjustability to fit you better. I put a set on my son's Sirrus to give him some flexibility in hand positions, and he likes them a lot. Not sure how it will work with the geometry of the 7100 but I don't think it should be a problem. They should fit just fine.

Cool, that's what I'm looking for, more hand positions and better aerodynamics for when there is a massive headwind, though ~100 bucks is alot for such an add-on. Maybe I can pick up a set en ebay or wot-not. Thanks for the info sir.

The T2 bars are very similar and cost about $50.

Performance

Now that I look, the ones on my son's bike are the T2, I think I caught them on sale at about $30

I bought those exact same bars last week for $80 CDN total at my LBS. I would suggest not buying used aerobars off ebay, only new in box.

If you live close to the city, forget about aerobars. But if you live like me just on the edge of the city where it turns to rural roads/farmland then these will be a big help. Hasn't been a day where I haven't used them.

The only niggly about installing aerobars is that you may have to get the addon computer mount that goes in the middle. I didn't have to because my DB4LW just fit right next to it and I added an extra extension arm so I could see it.

Set these up right, and they will be very comfortable, very useful.