<div class="mb-3" style="width: 22rem;">

  <select data-mdb-select-init data-mdb-size="lg">

    <option value="1">One</option>

    <option value="2">Two</option>

    <option value="3">Three</option>

    <option value="4">Four</option>

    <option value="5">Five</option>

    <option value="6">Six</option>

    <option value="7">Seven</option>

    <option value="8">Eight</option>

  </select>

</div>

​

<div class="mb-3" style="width: 22rem;">

  <select data-mdb-select-init>

    <option value="1">One</option>

    <option value="2">Two</option>

    <option value="3">Three</option>

    <option value="4">Four</option>

    <option value="5">Five</option>

    <option value="6">Six</option>

    <option value="7">Seven</option>

    <option value="8">Eight</option>

  </select>

</div>

​

<div class="mb-3" style="width: 22rem;">

  <select data-mdb-select-init data-mdb-size="sm">

    <option value="1">One</option>

    <option value="2">Two</option>

    <option value="3">Three</option>

    <option value="4">Four</option>

    <option value="5">Five</option>

    <option value="6">Six</option>

    <option value="7">Seven</option>

    <option value="8">Eight</option>

  </select>

</div>