ˈoʊk ˈæpəlz ɹˈeɪndʒ ɪn sˈaɪz fɹʌm ɪn daɪˈæmɪɾɚ ænd ɑːɹ kˈɔːzd baɪ kˈɛmɪkəlz ɪndʒˈɛktᵻd baɪ ðə lˈɑːɹvə ʌv sˈɜːʔn̩ kˈaɪndz ʌv ɡˈɔːl wˈɑːsp ɪnðə fˈæmɪli sˈɪnɪpˌɪdiː.
Oak apples range in size from  in diameter and are caused by chemicals injected by the larva of certain kinds of gall wasp in the family Cynipidae.