Yes, Actually this way these selct boxes also become small and just one option is seen at a time.
For reducing height to 30px, there is class .input-sm which can be used for reduding height to 30px. Its already default in bootstrap. But I think we don't have to add this class and use this height only. (which is now 34px).

![screenshot from 2014-04-17 17 34 41](https://cloud.githubusercontent.com/assets/1821959/2731204/8c2dac84-c628-11e3-93f3-4b1fbe6afd84.png)