ɪt ɹˈʌnz nˈɔːɹθ sˈaʊθ fɔːɹ θɹuː ðə tˈaʊnz ʌv ˈɪslɪp ænd smˈɪθtaʊn, kənˈɛktɪŋ ˌɛnwˈaɪ twˈɛnti sˈɛvən ˈeɪ ɪnðə tˈaʊn sˈiːt ʌv ˈɪslɪp tə ðɪ ˈiːst ˈɛnd ʌvðɪ ˌɛnwˈaɪ twˈɛnti fˈaɪv ænd ˌɛnwˈaɪ twˈɛnti fˈaɪv ˈeɪ kəŋkˈɜːɹənsi ɪn smˈɪθtaʊnz vˈɪlɪdʒ ʌvðə bɹˈæntʃ.
It runs north–south for  through the towns of Islip and Smithtown, connecting NY 27A in the town seat of Islip to the east end of the NY 25 and NY 25A concurrency in Smithtown's Village of the Branch.