  Physics from beyond the Standard Model, such as leptoquarks, can induce four
fermion operators involving a quark, an anti-quark, a lepton and an
anti-lepton. We update the (flavour dependent) constraints on the coefficients
of such interactions, arising from collider searches for contact interactions,
meson decays and other rare processes. We then make naive estimates for the
magnitude of the coefficients, as could arise in texture models or from inverse
hierarchies in the kinetic term coefficients. These estimates suggest that rare
Kaon decays could be a good place to look for such operators.
