govuk-frontend/dist/govuk/components/input/template-with-suffix.html

GOV.UK Frontend contains the code you need to start building a user interface for government platforms and services.

<div class="govuk-form-group">
  <label class="govuk-label" for="input-with-suffix">
    Weight, in kilograms
  </label>
  <div class="govuk-input__wrapper">
    <input class="govuk-input" id="input-with-suffix" name="weight" type="text">
    <div class="govuk-input__suffix" aria-hidden="true">kg</div>
  </div>
</div>