This cap is too small for you.I think a medium size will fit you better.

这顶帽子太小了，你戴不了。我想中号的会更适合你。

Do you have the medium size?

你这儿有中号的吗?

Yes.The blue one is a medium size.

是的。那顶蓝色的帽子就是中号的。

Let me try it on.

让我试试。

Sure.This one suits you much better.

好的。这顶更适合你。