Simple but effectiv and the perfect present for your italian mother-in-law ;o)
I meassured the diameters by myself with (standard) spaghetti (25 cm length / 0.2 cm diameter) for 100/200/300/and 400 g what are the quantities for 1/2/3 and 4 portions according to wikipedia.
There are two versions - a blank one and one with (very small) units at the rings.