Portion sizes in restaurants

[gozalim]

RC"N is definitely a different and bit larger shiur. Again, the smaller shiur of the Chazon Ish is 75 ml - half of his double shiur of 150 ml. As I said that was the commonly accepted minimum shiur in Galicia/Hungary at least pre war, the shiur that Reb Meir Arik writes, the Peschei Zita etc etc and was given over by the Satmar Rov as well. Then came RCN and researched it on his own and came up with his 86 ml shiur. The Chazon Ish strongly accepted the double shiur of the Tzlach (so that's commonly referred to as shiur Chazon Ish) but the world did not, as is also evident by the smaller bechers of previous Gedolim which most didn't contain 150 ml. For some odd reason there are some who mistakenly interpret that the smaller shiur alternative to Chazon Ish is by default the 86 ml shiur of RCN, perhaps the כוס-כוס הגון numerical value thing is to blame for that. 

the more likely reason for these 2 being the Default is not the gematria games but the fact that they both wrote (and researched) extensively on the topic of all shiurim, at a similar time. So they represent 2 approaches to shiurim

[EliJelly]

true, but in his post he clearly was aiming for a reviis

Which is the halacha too, since all achronim are cholek on the Taz, including the Alter Rebbe. (Not going into the Ropshitz mesorah here)

the more likely reason for these 2 being the Default is not the gematria games but the fact that they both wrote (and researched) extensively on the topic of all shiurim, at a similar time. So they represent 2 approaches to shiurim

Half true. Because in the Chazon Ish's shiur is also included the 75 ml smaller shiur since his 150 is based on the Tzlach so the majority of achronim who didn't accept the נתקטנו הביצים theory are left with his half shiur of 75. Ignoring that is quite ignorant. 

[imayid2]

Interestingly, there are eggs recovered from Pompei which support the smaller shiur

[imayid2]

Everyone makes a bracha achrona on the smaller shiur but when it comes to challah all of the sudden no one will make a bracha on the smaller shiur. Weird.

[TzviR]

https://www.walmart.com/ip/Better-Homes-Gardens-4-Count-Stainless-Steel-Shot-Glasses-in-Black-Gunmetal-Finish/347048601?athAsset=eyJhdGhjcGlkIjoiMzQ3MDQ4NjAxIiwiYXRoc3RpZCI6IkNTMDIwIiwiYXRoYW5jaWQiOiJJdGVtQ2Fyb3VzZWwiLCJhdGhyayI6LTAuMzk1MDIwOH0=&athena=true