prevent vertical expansion of a select box using Select2

[arclite...@gmail.com]

`<select name="assignto" type="text" class="mselects" multiple="multiple" style="width:460px; overflow:hidden;">
<option value="01234567,John Williams">Tech - John Williams</option>
<option value="02568747,Steve Jobs">Tech - Steve JObs</option>
<option value="48587957,Jessie Malts">Admin - Jessie Malts</option>
</select>`

In the case of this field above, if I were to add more options and the user were to add greater than 3 selections the SELECT box is expanding vertically to accommodate the selections. How can I prevent the the vertical expansion of the SELECT when the number of selections exceeds the width of the SELECT box?