Ff phages are composed of circular single-stranded DNA (ssDNA), which in the case of the m13 phage is 6407 nucleotides long and is encapsulated in approximately 2700 copies of the major coat protein p8, and capped with about 5 copies each of four different minor coat proteins (p3 and p6 at one end and p7 and p9 at the other end).

The life cycle is relatively short, with the early phage progeny exiting the cell ten minutes after infection.

The coat's dimensions are flexible because the number of p8 copies adjusts to accommodate the size of the single stranded genome it packages.

These proteins are very small, containing only 33 and 32 amino acids respectively, though some additional residues can be added to the N-terminal portion of each which are then presented on the outside of the coat.

[12] George Smith, among others, showed that fragments of EcoRI endonuclease could be fused in the unique Bam site of f1 filamentous phage and thereby expressed in gene 3 whose protein p3 was externally accessible.

This can be used to assemble structures like gold or cobalt oxide nano-wires for batteries[14] or to pack carbon nanotubes into straight bundles for use in photovoltaics.