  In the context of spontaneous wave function collapse models, we investigate
the properties of the Continuous Spontaneous Localization (CSL) collapse rate
for rigid bodies. By exploiting the Euler-Maclaurin formula, we show that for
standard matter the rate for a continuous mass distribution accurately
reproduces the exact rate (i.e. the one for a point-like distribution). We
compare the exact rate with previous estimates in the literature and we asses
their validity. We find that the reduction rate displays a peculiar mass
difference effect, which we investigate and describe in detail. We show that
the recently proposed layering effect is a consequence of the mass difference
effect.
