Shalom, I recently read a book written by Harav Beinish, describing the two opinions about Reviit. One was of the Chazon Ish, according to him Reviit is 150 cc, and the other one is of Harav Na’eh, who holds that Revi’is is 86.4 cc. Harava Beinish writes that 86.4 cc is not accurate, and should be 75 cc instead. Harav Hadar Yehuda Margolin writes the same. Ie, not 86.4, but 75 cc. For those that used to hold 86.4, is the Halacha 86.4, or 75 cc? B’Chavod Rav,

To clarify the issue a bit, Rav Chaim Naeh set out to support the existing minhag that was essentially based on a coin called a ‘dirham’ which was used commonly as a certified weight. This coin was used extensively as a standard measure of weight throughout the Middle East from the times of the Rambam, who quotes it as the means of measuring halachic quantities. While Rav Naeh was fighting this cause, the Ottoman Empire was crumbling, and the dirham lost its stability. Unknowingly, the dirham Rav Chaim Naeh was using as a standard measure was roughly 10% larger than it was over the centuries, which threw him off a bit. Interestingly enough, Chazon Ish, who held the measurements should be doubled, did not double Rav Chaim Naeh’s measurements based on the dirham, but rather what actually fit other standards, i.e. 75 cc. On a personal note, years back I used to sell eggs and measured dozens of them, finding that eggs are naturally around 50cc, putting the Reviit at 75cc (nowadays chickens are treated to grow large eggs and therefore the standard egg is almost 60cc which would fit Rav Chaim Naeh’s measurement). Since Rav Chaim Naeh’s halachic reasoning is based on the tradition of the dirham, and we know for certain that the dirham was actually smaller, Rav Chaim Naeh would surely agree that the Reviit should be 75cc. May our midos match the Torah’s true standards, Rabbi Yochanan Lombard