CAS 57-91-0 appears in our catalog under these names: Estradiol EP Impurity B (Ethinylestradiol EP Impurity L, 17-epi-Estradiol), Estradiol Impurity 2(Estradiol EP Impurity B), Ethinylestradiol Impurity 12（Ethinylestradiol EP Impurity L）, 17alpha-Estradiol, >95% (HPLC), Estra-1,3,5(10)-triene-3,17alpha-diol (17alpha-Estradiol, 17-epi-Estradiol). Offered by: Chemat Brand, Hubei YoungXin, TRC, Mikromol, Dr. Ehrenstorfer. Available pack sizes: on request, 10mg, 25mg, 50mg, 100mg, 200mg, 250mg, 1ml.