ionic-framework/ionic/components/button/test/clear/main.html

<ion-toolbar>
  <ion-title>Clear Buttons</ion-title>
</ion-toolbar>

<ion-content padding style="text-align:center">

  <p>
    <button class="button-clear">Default</button>
    <button class="button-clear activated">Default.activated</button>
  </p>

  <p>
    <button class="button-clear-primary">Primary</button>
    <button class="button-clear-primary activated">Primary.activated</button>
  </p>

  <p>
    <button class="button-clear-secondary">Secondary</button>
    <button class="button-clear-secondary activated">Secondary.activated</button>
  </p>

  <p>
    <button class="button-clear-danger">Danger</button>
    <button class="button-clear-danger activated">Danger.activated</button>
  </p>

  <p>
    <button class="button-clear-light">Light</button>
    <button class="button-clear-light activated">Light.activated</button>
  </p>

  <p>
    <button class="button-clear-dark">Dark</button>
    <button class="button-clear-dark activated">Dark.activated</button>
  </p>

</ion-content>