Wheel Spacer

Hey I have 2 , 12.5 MM Spacers and wanted to know what length Studs i should be Replacing them with.
The stock Length is 40 MM ( I think ) 
And there are a max Length of 50 MM on ebay for Sale. Can anyone help me on this so i can make the right purchase. 
Or is there any other provider for Lexus Wheel studs?

Thanks for all the Help Guy's .............................................
Well i got my Wheel studs.
I got 55MM Studs 
Which the originals were - 45 MM
so i think this will give me enough to Bolt them on and maybe even Get a little more if they are not quit right.
I will post the results

so it is finally Flush, 
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