N,N-Bis(PEG2-N3)-N-amido-PEG2-thiol serves as a cleavable 4 unit PEG ADC linker in the preparation of antibody-drug conjugates (ADCs) [1]. This compound functions as a click chemistry reagent, equipped with an Azide group, allowing it to participate in copper-catalyzed azide-alkyne cycloaddition reactions (CuAAc) with alkyne-bearing molecules. Additionally, it is capable of engaging in strain-promoted alkyne-azide cycloaddition (SPAAC) with molecules that contain DBCO or BCN groups.