Mal-PEG4-bis-PEG3-methyltetrazine is a cleavable 7 unit PEG ADC linker used in the synthesis of antibody-drug conjugates (ADCs). Mal-PEG4-bis-PEG3-methyltetrazine is a click chemistry reagent, it contains a Tetrazine group that can undergo an inverse electron demand Diels-Alder reaction (iEDDA) with molecules containing TCO groups.