TT #185 · Parshas Shemini · Aliyah 5 · Passuk 32
Chabad.org — Vayikra Chapter 11 with Rashi
English: “Or sack”: the rule is not limited to material made from goats; it also includes material made from a horse’s tail or a cow’s tail.
Shabbos 64a.
E-Daf.com — Shabbos 64a (Tsurras Hadaf)
Textual inclusion — The word “sack” broadens the category beyond one particular source of fiber.
Horse-tail and cow-tail materials are included.