<!DOCTYPE html>
<html lang="id">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
<title>Bootstrap Custom Select Menu Sizing</title>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.min.css">
<script src="https://code.jquery.com/jquery-3.5.1.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.1/dist/umd/popper.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.0-beta3/dist/js/bootstrap.bundle.min.js"></script>
<style>
    .bs-example{
        margin: 20px;        
    }
</style>
</head>
<body>
<div class="bs-example">
    <form>
        <select class="custom-select custom-select-lg">
            <option selected> Menu pilih kustom besar </option>
            <option value="1">Satu</option>
            <option value="2">Dua</option>
            <option value="3">Tiga</option>
        </select>
        <select class="custom-select mt-3">
            <option selected> Menu pilihan kustom default</option>
            <option value="1">Satu</option>
            <option value="2">Dua</option>
            <option value="3">Tiga</option>
        </select>
        <select class="custom-select custom-select-sm mt-3">
            <option selected> Menu pilih kustom kecil </option>
            <option value="1">Satu</option>
            <option value="2">Dua</option>
            <option value="3">Tiga</option>
        </select>
    </form>
</div>
</body>
</html>

External CSS

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External JavaScript

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