Ghost/ghost/admin/app/components/modal-enable-tiers.hbs

<header class="modal-header">
    <h1>Tiers is a one-way street!</h1>
</header>
<a class="close" href="" role="button" title="Close" {{action "closeModal"}}>{{svg-jar "close"}}<span class="hidden">Close</span></a>

<div class="modal-body">
    <p>Tiers for paid memberships is currently in an early access beta. Once enabled, it cannot be switched off. <a href="http://ghost.org/help/tiers" target="_blank">Learn more here</a></p>
</div>

<div class="modal-footer">
    <button {{action "closeModal"}} class="gh-btn"><span>Cancel</span></button>
    <button {{action "confirm"}} class="gh-btn gh-btn-primary"><span>Enable Tiers</span></button>
</div>