Reduce size of dropdown in Bootstrap 3

I want to reduce the height of input fields. So, I have created a css class

.input-field {
  height: 20px
}

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This works fine for text fields and also reduces the height of drop downs. However, in drop down the selection text is cut. How can I ensure that the complete text inside the drop down is visible

Here is the fiddle - https://jsfiddle.net/zvn3wknj/

The selection text 'Approve' and 'Reject' is cut and not displayed correctly.