A ready to use kit for the labeling of antibodies with sulfo-Cyanine 3 dye, a Cy3® equivalent. This kit contains all necessary components (chemicals and consumables) to perform 10 labelings of antibodies (up to 100 µg of antibody per each reaction). Reaction clean up is achieved using enclosed gel filtration spin columns. Precise quantification of the dye guarantees reproducible outcome of the labeling and number of fluorophores per antibody molecule. Purified labeled antibodies are available in PBS buffer after 40 min (10 min hands-on time). The kit tolerates common additives such as Tris, glycerol, and sodium azide.