AAT Bioquest's iFluor® dyes are developed for labeling proteins, in particular, antibodies. These dyes are optimized to have minimal fluorescence quenching effect on proteins and nucleic acids. Our iFluor® 633 dyes have fluorescence excitation and emission maxima close to ~633 nm and ~655 nm respectively with good photostability. Our in-house comparable studies indicated that our iFluor® 633 dyes are significantly brighter than the corresponding Cy5®. These spectral characteristics make them a superior alternative to Cy5® and Alexa Fluor®633 (Cy5® and Alexa Fluor® are the trademarks of GE Healthcare and Invitrogen respectively). iFluor® 633 conjugates have been widely used in fluorescence animal imaging applications. ReadiLink™ labeling kits essentially only require 2 simple mixing steps without a column purification needed. iFluor® 633 SE used in this ReadiLink™ kit is reasonably stable and shows good reactivity and selectivity with protein amino groups. The kit has all the essential components for labeling ~2x50 ug antibody. Each of the two vials of iFluor® 633 dye provided in the kit is optimized for labeling ~50 µg antibody. iFluor® 633 SE protein labeling kit provides a convenient method to label monoclonal, polyclonal antibodies or other proteins (>10 kDa) with the iFluor® 633 SE.