Select wide uses the input--block class to produce a 100% width variant.
<div class="field field--select">
<label class="label venus " for="select-wide">
Select your favourite cartoon character
</label>
<select class="input input--select input--block" id="select-wide" name="select">
<option selected disabled>Select an option</option>
<option value="bart">Bart Simpson</option>
<option value="homer">Homer Simpson</option>
<option value="marge">Marge Simpson</option>
<option value="lisa">Lisa Simpson</option>
<option value="ned">Ned Flanders</option>
<option value="bugs">Bugs Bunny</option>
<option value="7 Dwarves">The 7 Dwarves: Grumpy, Happy, Sleepy, Bashful, Sneezy, Dopey & Doc</option>
<option value="charlie brown">Charlie Brown</option>
<option value="snoopy">Snoopy</option>
</select>
</div>
{
"label": "Select (wide)",
"label_text": "Select your favourite cartoon character",
"label_for": "select-wide",
"label_description": null,
"select_classes": " input--block",
"options": [
{
"option_text": "Select an option",
"option_value": null,
"selected": "selected",
"disabled": "disabled"
},
{
"option_text": "Bart Simpson",
"option_value": "bart"
},
{
"option_text": "Homer Simpson",
"option_value": "homer"
},
{
"option_text": "Marge Simpson",
"option_value": "marge"
},
{
"option_text": "Lisa Simpson",
"option_value": "lisa"
},
{
"option_text": "Ned Flanders",
"option_value": "ned"
},
{
"option_text": "Bugs Bunny",
"option_value": "bugs"
},
{
"option_text": "The 7 Dwarves: Grumpy, Happy, Sleepy, Bashful, Sneezy, Dopey & Doc",
"option_value": "7 Dwarves"
},
{
"option_text": "Charlie Brown",
"option_value": "charlie brown"
},
{
"option_text": "Snoopy",
"option_value": "snoopy"
}
]
}