All fibres for 4MOST are silica/silica, step-index, multi-mode fibres with polymide coating (buffer), with broad-band transmission from 350-2000 nm and numerical aperture (NA) of 0.22. However, the dimensions of fibres differ depending on their function in the 4MOST Fibre System (science, fiducial, calibration, guide, and back-illumination fibres) and have been selected accordingly. The described fibres are a common choice for astronomical spectrographs, and therefore a large amount of test and on-sky data exists to judge their performance in advance.