The isobaric labels TMT (tandem mass tagging) are available in up to 11 tags that can be used for labeling practically any peptide or protein sample. TMT makes it possible to multiplex the analysis, to efficiently use the instrument time and exert further controls for technical variation. Due to its ability to multiplex up to 11 samples, TMT are widely used for quantitative protein biomarker discovery. TMTzero, TMTduplex, TMTsixplex, TMT10plex, and TMT11plex Reagents share an identical structure, allowing efficient transition from methods development to multiplex quantitation.