Level 1: .col-sm-9 Level 2: .col-xs-8 .col-sm-6 Level 2: .col-xs-4 .col-sm-6 Level 1: .col-sm-3 Level 1: .col-sm-9 Level 2: .col-xs-8 .col-sm-6 Level 2: .col-xs-4 .col-sm-6 Level 1: .col-sm-3