What should we call this drop-down alternative?

Reading this article on better form design, one of its tips is to "Show all selection options if under 6", as opposed to hiding the options in a dropdown list.

See this example they provide:

I've seen this pattern before and intuitively understood it, but somehow I never thought of it as an alternative to dropdowns. I don't think it's a hard and fast rule to say "under 6", but it is a helpful tool to add to our toolbox.

I want to document this pattern in our library but I don't know what to call it.

Bootstrap documents how to convert buttons into checkboxes or radio buttons, but doesn't give this option a succint name. Material doesn't cover this in their components guidelines.

What would you call this?