DBCO-PEG3-SS-NHS ester is a cleavable 3 unit PEG ADC linker used in the synthesis of antibody-drug conjugates (ADCs). DBCO-PEG3-SS-NHS ester is a click chemistry reagent, it contains a DBCO group that can undergo strain-promoted alkyne-azide cycloaddition (SPAAC) with molecules containing Azide groups.