Select

Bootstrap Select boxes are styled with the .form-select[-*] classes.
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<!DOCTYPE html><html>
<head><link href='https://cdn.jsdelivr.net/npm/bootstrap@5.2.0-beta1/dist/css/bootstrap.min.css' rel='stylesheet' integrity='sha384-0evHe/X+R7YkIZDRvuzKMRqM+OrBnVFBL6DOitfPri4tjfHxaWutUpFmBp4vmVor' crossorigin='anonymous'>
      <script src='https://cdn.jsdelivr.net/npm/bootstrap@5.2.0-beta1/dist/js/bootstrap.bundle.min.js' integrity='sha384-pprn3073KE6tl6bjs2QrFaJGz5/SUsLqktiwsUTF55Jfv3qYSDhgCecCxMW52nD2' crossorigin='anonymous'></script>
      <style>div:not(.container):not(.tooltip):not(.tooltip *):not(.navbar *):not(.carousel-caption):not(.card *):not(.form-check):not(.input-group) { border:1px solid grey; text-align:center; }</style>
</head><body>

   <select class="form-select form-select-lg mb-3" aria-label=".form-select-lg example">
      <option selected>Open this large select menu</option>
      <option value="1">One</option>
      <option value="2">Two</option>
      <option value="3">Three</option>
   </select>
   <select class="form-select" aria-label="Default select example">
      <option selected>Open this default select menu </option>
      <option value="1">One</option>
      <option value="2">Two</option>
      <option value="3">Three</option>
   </select><br/>
   <select class="form-select form-select-sm" aria-label=".form-select-sm example">
      <option selected>Open this small select menu</option>
      <option value="1">One</option>
      <option value="2">Two</option>
      <option value="3">Three</option>
   </select>

</body><html>