CAS 721431-18-1 appears in our catalog under these names: Biotin–PEG4–acid, Biotin-PEG(4)-COOH, Biotin-PEG(24)-COOH, Biotin-PEG(48)-COOH, Biotin-PEG4-propionic Acid, >98.0%(T). Offered by: GLPBio, Iris Biotech, TCI, Biosynth, Ambeed. Available pack sizes: 100mg, 50mg, 1g, 250mg, 1000mg, 25mg, 5g, 10g.