if you have strong arms (or are an experienced cyclist) a larger drop is ok, but if you have weak little girly arms like me (or, again, you're new to riding) you'll want something with a straighter hand position. I have nitto RB021's and the bend wreaks havoc on the elbows, and makes skidding a bit more difficult. The 38cm, 40cm, 42cm, etc... is referring to the width. I always find I'm most comfortable with a midwidth bar, so around 40cm or so...