t-Boc Amine PEG Succinimidyl Carboxymethyl Ester (t-Boc Amine PEG SCM) is a linear heterobifunctional PEG derivative commonly used as a crosslinker or spacer between two different chemical entities. The PEG moiety in heterofunctional PEG derivatives provides water solubility, biocompatibility and flexibility. Applications are particularly suited for the development of antibody drug conjugates (ADCs).