10.00mm x1.0 thread pitch bubble flare for the master cylinder ports.

https://www.linestogo.com/civic-brak...gaAoPMEALw_wcB

You might be better off just ordering a premade line kit, especially if you want stainless because the flaring tools required are expensive, the normal double flare tool you get at the parts store will break on the 1st try.


Also keep in mind the stock material lasted almost 20 years.