CAS 21876-43-7 appears in our catalog under these names: 4–(Pyridin–1–ium–1–yl)butane–1–sulfonate, 4-(Pyridin-1-ium-1-yl)butane-1-sulfonate, 98%, N-(4-Sulfobutyl)pyridinium inner salt, 97%, 4-(Pyridin-1-ium-1-yl)butane-1-sulfonate, 97%. Offered by: GLPBio, Ambeed, Chemat, BLDpharm, Fluorochem. Available pack sizes: 100g, 25g.