Ok got it, I need to edit tailwind.config.js and set custom sizes there. For example:
height: [
...
'278px': '278px',
...
]
So now this size can be set with <div clas="h-278px">...</div>
Update:
After completed many projects on top of TailwindCSS I learned that it’s not very optimal to set spacing/w/h… in tailwind config if it’s used only once. It’s better to go with the custom class you can always use @apply in that class anyway.
Update 2021:
As of tailwind version 2.1 we can enable JIT and use arbitrary styles like this:
mb-[278px]