bootstraps col nesting inherits main col style - css

Question

I'm building a layout for my login page and am having problem getting my buttons to line up. I have used a custom class to center my username and password form, and would now like to have 2 equal sized buttons for log in and sign up underneath them. I tried achieving this with col that are half size of the parent, but so far they are just sized the same. Any help on what I'm doing wrong is appreciated.
html:
<div class="col-xs-4 centered">
<%= form_tag sessions_path do %>
<div class="form-group">
<%= label_tag :email %>
<%= text_field_tag :email, params[:email], class:'form-control' %><br/>
<%= label_tag :password %>
<%= password_field_tag :password, nil, class:'form-control' %><br/>
<div class="col xs-2">
<%= submit_tag "Log in", class:'btn btn-primary btnstyle' %>
</div>
<div class="col xs-2">
<%= link_to 'Sign Up', new_user_path, class:'btn btn-primary btnstyle' %>
</div>
<% end %>
</div>
</div>
css:
.btnstyle {
width:100%;
}
.centered {
float: none;
margin: 0 auto;
}
I tried to set up a fiddle, but ofc it won't work with rails tags...

Answer 1

figured it out, had a - missing and had to post them outside of the main col with an offset to center. Here's the final result:
<div class="col-xs-4 centered">
<%= form_tag sessions_path do %>
<div class="form-group">
<%= label_tag :email %>
<%= text_field_tag :email, params[:email], class:'form-control' %><br/>
<%= label_tag :password %>
<%= password_field_tag :password, nil, class:'form-control' %><br/>
</div>
</div>
<div class="col-xs-2 col-xs-offset-4">
<%= submit_tag "Log in", class:'btn btn-primary btnstyle' %>
</div>
<div class="col-xs-2">
<%= link_to 'Sign Up', new_user_path, class:'btn btn-primary btnstyle' %>
</div>
<% end %>
</div>