Left: Small-scale magnetic field of M dwarfs as a function of rotation period. Red hexagons and blue stars indicate literature (Morin et al. 2010; Shulyak et al. 2017) measurements for stars in dipole and multi-pole states, respectively. The six M dwarfs in this work are shown with the same symbols, fully opaque, with their names indicated on the plot. The symbol size scales with stellar mass (see scale), and the horizontal dashed line shows the 4 kG saturation threshold associated with stars in a multi-pole dynamo regime. Right: Ratio of the magnetic fluxes recovered from Stokes V to Stokes I measurements as a function of rotation period. The same symbols and colour-coding are used as in the left panel, and the horizontal dashed lines indicate the mean fraction of magnetic flux detected in Stokes V spectra (6% and 14%).