lˈeɪt pˈætɚn ˌeɪtʃkˈeɪ fˈoːɹɾi wˈʌn z ænd ˌeɪtʃkˈeɪ nˈaɪnti wˈʌn z ɑːɹ vˈɜːtʃuːəli aɪdˈɛntɪkəl ɪn ɐpˈɪɹəns ɛksˈɛpt fɚðə ɹᵻsˈiːvɚ mˈɑːɹkɪŋz ænd ðə ɹᵻtˈeɪnɪŋ hˈoʊl ʌvðə kˈɑːkɪŋ tˈuːb ˈɛnd kˈæp ænd ˈɔːl ðɛɹ pˈɑːɹts ɑːɹ ˌɪntɚtʃˈeɪndʒəbəl.
Late pattern HK41s and HK91s are virtually identical in appearance (except for the receiver markings and the retaining hole of the cocking tube end cap) and all their parts are interchangeable.