Reference for Kelim 16:4
כְּלֵי עוֹר, מֵאֵימָתַי מְקַבְּלִין טֻמְאָה. הַתּוּרְמֵל, מִשֶּׁיַּחְסֹם וִיקַנֵּב וְיַעֲשֶׂה קִיחוֹתָיו. רַבִּי יְהוּדָה אוֹמֵר, מִשֶּׁיַּעֲשֶׂה אֶת אָזְנָיו. סְקֹרְטְיָא, מִשֶּׁיַּחְסֹם וִיקַנֵּב וְיַעֲשֶׂה אֶת צִיצָתָהּ. רַבִּי יְהוּדָה אוֹמֵר, מִשֶּׁיַּעֲשֶׂה אֶת טַבְּעוֹתֶיהָ. קָטָבוֹלְיָא, מִשֶּׁיַּחְסֹם וִיקַנֵּב. רַבִּי יְהוּדָה אוֹמֵר, מִשֶּׁיַּעֲשֶׂה אֶת קִיחוֹתֶיהָ. הַכַּר וְהַכֶּסֶת שֶׁל עוֹר, מִשֶּׁיַּחְסֹם וִיקַנֵּב. רַבִּי יְהוּדָה אוֹמֵר, מִשֶּׁיִּתְפְּרֵם וִישַׁיֵּר בָּהֶם פָּחוֹת מֵחֲמִשָּׁה טְפָחִים:
When do leather vessels become susceptible to impurity? A leather pouch, as soon as he stitches its hem, and smooths its rough ends and makes its straps. Rabbi Yehudah says: so soon as he makes its ears. A leather apron [becomes susceptible to impurity] as soon as he stitches its hem, and smooths its rough ends and makes its strings. Rabbi Yehudah says: as soon as he makes its loops. A leather bed cover [becomes susceptible] as soon as he stitches its hem and smooths its rough ends. Rabbi Yehudah says: as soon as he makes its straps. A leather cushion or mattress [becomes susceptible] as soon as he stitches its hem and smooths its rough ends. Rabbi Yehudah says: as soon as he sews it up and leaves open less than five <em>tefachim</em>.