Master Cylinder, I can't find the right one!

I have a 2005 Aveo Hatchback LS / Automatic without ABS. For the life of me I can't find a master cylinder for it. I check Autozone and Orilley and they both have it in stock but none matches my car. By that I mean the 2 larger ports on the bottom of the MC won't fit the adapter fittings off the original. The opening on the MC is smaller than the fitting on the car. I even tried a manufactured MC with the same results. The counter guys are baffled by this because the reman has the same stamp and number as the original. Has anyone ran across this?? I checked with my dealer and this part has been discontinued from GM. The GM part number they came up with is 93742291. Even the dealer used this part number with Orielly and had the same problem. The larger ports on the MC were smaller than the fittings. I wonder if the MC had been replaced before with a different model year? Any help on this would be greatly appreciated.

These are the two adapters in question off the original master cylinder (black).

Attachment 10291Attachment 10292

Picture of the master cylinder off the car.

I am thinking the port size are 16mm. See how it goes..

Attachment 10293

Okay ladies and gents.. If you find yourself in the same situation as I was not knowing what is the port valve size for my master cylinder then here's my solution. Do what I did and take the fitting in question to Home Depot. Go to the Hardware/Fasteners department and look for a gauge that is on the wall that has all the nut sizes. It will have all types of nut sizes that give you what sizes they are in millimeters. Of course threading will be different but it gives you an idea what you are looking for. In this case mine was 16mm port valve. Ordered the part on the internet with the corresponds size and bam you got it! Part came in today and it fits. Done deal!!! From what I saw I did see other sizes for the same model year of my car as follows.


16mm, 15mm and finally 10mm. Again this are the "large" ports sizes on the bottom of the master cylinder, there are two of them. Based on my local parts store I guess the popular MC for my area is 10mm. This holds true with my local Chevy dealer and came up with the part number for a 10mm as well using the VIN#. Why my Aveo was 16mm??? No clue.. I was very close to ordering one from the internet which was 10mm based on the GM part number. Glad I didnt and just went to the hardware store instead lol.. I hope this helps some people.