  Assuming one nonzero product of two $\lambda'$-type couplings and working in
two different bases for the left-handed quark superfields, the neutral meson
mixings are used to bound these products. We emphasize the strong basis
dependence of the bounds: in one basis many products contribute to neutral
meson mixings at tree level, while in the other these products except one
contribute at 1-loop level only and the GIM mechanism takes place.
Correspondingly, these bounds differ between bases by orders of magnitudes.
