Forms tail fibers that play a role in primary attachment of virion to host receptors. Assembles with Tail fiber assembly protein to form fibers attached to virion tail tip. Fibers are about 35nm long and have a thin, uniform diameter. There are presumaby six fibers per virion. They bind in a reversible manner to host molecules, attaching transiently the virion to the host until tail tip interacts with LamB and injects viral DNA into the cell. Interacts with Tail fiber assembly protein. Belongs to the tail fiber family. The current laboratory strain of bacteriophage lambda are descendants of a recombinant, lambdaPaPa derived from cross between strains lambda Pasadena (Caltech) and Paris (Institut Pasteur). These stains carry a frameshift mutation relative to lambda originally derived from the original K12 E-Coli strain, called Ur-lambda. The Ur-lambda virions have thin, jointed tail fibers (side tail fibers) that are absent from lambda wild-type. Relative to lambda PaPa, Ur-lambda has expanded receptor specificity and adsorbs to E.coli cells more rapidly.