Page Builder 
Widgets Bundle 
SiteOrigin CSS 
Installer 
Remove panel-grid and panel-grid-cell classes using a filter
developerpluginplugin-widgets-bundle · By Matthew Gross · 10 years ago · Reply by Alex S 9 years ago
The classes I'd like to remove are 'panel-grid' and 'panel-grid-cell'. The classes for the custom grid are then added using the siteorigin panels row cell classes filter.