We have recently update to version 7.0.0 of Telerik for Blazor controls.
We have also access to Progress ThemeBuilder application which we use to customize the default Material theme.

After the update to version 7 and also upgrading and compiling the new theme file for our application, TabStrip items fail to display the correct css and defaults to the theme's original css.

ThemeBuilder produces rules for the tab item items with the following path

.lvs-tabstrip.k-tabstrip .k-tabstrip-items-wrapper .k-tabstrip-items.k-reset.k-tabstrip-items-start .k-item.k-tabstrip-item

where the actual control generates the following

.lvs-tabstrip.k-tabstrip .k-tabstrip-items-wrapper .k-tabstrip-items.k-reset.k-tabstrip-items-start .k-item

As you can see it is missing the k-tabstrip-item class and the custom theme fails to render correctly. Either Telerik blazor libary did not add this extra class to each tab item or theme builder is inserting this class when it should not. 

I can place this extra class on each TabStripTab element on its Class property, but I feel this is something that the actual Telerik for Blazor libray should do.

Looking at the source code of Telerik for Blazor library, the TabStipTab component generates add the k-item as default and then applies the value of property ClassToRender and its value is 

$"{ActiveCssClass} {DisabledCssClass} {Class} {FirstItemClass} {LastItemClass}".Trim()

The Class is an empty string, which I currently use to "fix" the problem but I certainly would like a better solution like a real fix :) 

Thank you telerik team