How do I set CSS3 flex-basis property using Bootstrap Flex?

Using CSS3 I can individually set the flex properties like so

.someclass {    flex-grow: 1;    flex-shrink: 1;    flex-basis: auto;   }

Using Bootstrap (version >= 4.1) flex it seems I can only set flex-grow-X and flex-shrink-X, like so

<div class="someclass flex-grow-1 flex-shrink-1">...</div>

Is there are way to set the flex-basis using bootstrap 4.1?