I bought the GC2 for my mountain bike. I had bar ends on it before but I decided that the GC2 with it's built-in bar end had a cleaner look. It allows you to position your hands a little differently on the end, turning your fingers to the outside, if you want a change of grip. I can only wrap two fingers around the bar end for climbing or accelerating so they aren't much for that, but better than nothing. They are also enough to hold my headlight off of the ground when I turn the bike upside down to work on something. :-) I like them, but I have some trekking bars coming that I want to play with, so I'll probably get a pair of GP1s to go on that. I haven't decided yet.

As for size, I bought mine in a lbs so I could grab them and see what I liked. I have long fingers so ended up with the larger size.