  Magnetic activity and rotation are known to be intimately linked for low-mass
stars. Understanding rotation evolution over the stellar lifetime is therefore
an important goal within stellar astrophysics. In recent years, there has been
increased focus on how the complexity of the stellar magnetic field affects the
rate of angular momentum-loss from a star. This is a topic that Zeeman-Doppler
imaging (ZDI), a technique that is capable of reconstructing the large-scale
magnetic field topology of a star, can uniquely address.
  Using a potential field source surface model, we estimate the open flux, mass
loss-rate and angular momentum-loss rates for a sample of 66 stars that have
been mapped with ZDI. We show that the open flux of a star is predominantly
determined by the dipolar component of its magnetic field for our choice of
source surface radius. We also show that, on the main sequence, the open flux,
mass- and angular momentum-loss rates increase with decreasing Rossby number.
The exception to this rule is stars less massive than $0.3M_{\odot}$. Previous
work suggests that low mass M dwarfs may possess either strong, ordered and
dipolar fields or weak and complex fields. This range of field strengths
results in a large spread of angular momentum-loss rates for these stars and
has important consequences for their spin down behaviour. Additionally, our
models do not predict a transition in the mass-loss rates at the so called wind
dividing line noted from Ly$\alpha$ studies.
