Would someone be able to tell me what size are the 2 washers (part #901-355-936-00-OEM) are that sit inside the m/c reservoir feed line holes? Do they sit inside the bottom ridge.? Thanks in advance.

I thought I had the washers sitting in the old MC I replaced a couple years back to measure, but when I look now, they aren't there, unfortunately. But, yes, they do sit in the bottom of the feed inlet ports.

The ones Stoddard sells are 8 x 10mm

https://www.stoddard.com/90135593600.html.html

I get them from the dealer. No shipping charges

You mean at the banjo fitting? 8mm or 5/16". Copper preferred. I just put a bunch of banjo fittings on my car... Boxster calipers, T banjos at M/C and at rear bulkhead.

I’m pretty sure it’s the spacer washer that fits under the metal lines that go into the top of the master cylinder. Leave them out and the fluid will eventually leak out. They usually come with new mc’s or reuse the old ones.

The 8mm x 10mm seems small, is this ridge or shoulder where the washer should fit into? This would elevate it about 2mm from the reservoir supply fittings floor.Click to view attachment

Yes

Ok I now understand where the washer needs to go, bear with me here. I removed a 19mm M/C out of my car today because ... well it looked like ithad been used as an anchor, previous owner put it in. I have on order a new MC but wasn't sure if it would come with washers so I checked the old one .... none, plus one of the two interior seals was backwards so I know why it looked the way it did. Now I asked my original question because I thought maybe I could find some, somewhere. The 19mm step measured at 14.35mm, in one of my drawers I actually found two washers that fit perfectly (14.25mm). Now when you guys said 8x10mm I thought I had the wrong area for the washer. I dug around and found the original 17mm MC and it did have washers... 13.95mm and confirmed that step in the pic. Now I realize the 17mm is oem and the19mm is aftermarket but there is only one part number from porsche. Sorry for rambling...Click to view attachment

The new Master cylinders come with new rubber, but not washers Got them if you need one