The present invention provides for a library of vectors comprising human HC-CDR3 regions of varying length, wherein the diversity of said library is focused on the HC-CDR3 region only and diversity has been optimized such that redundancy is reduced for short HC-CDR3 loops and coverage of HC-CDR3 region variants for longer loop lengths has been increased. The library of the present invention is displayed on phage for selection against target antigens.
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