As already mentioned, you shouldn't buy ski boots without trying them
on. but to answer you're question, just about every boot manufacturer
uses the same shell for 1/2 sizes, ie. a 28.0 is the same shell as a
28.5, a 29.0 is the same shell as a 29.5. etc.
they make up the difference with either a thicker liner, or a higher
footbed.