[Need_for_speed]

Jay, fair question.
Here's what Fred had to say (Woody's Build Thread):

" Correct. My 2cents RE spacers:

I actually make those “custom” for teams and other track cars here (not only Porsche) and have a little business going on in JP also. We get orders in the 13mm spacers as much as we get them in the 18mm and do custom adapters also. For info the Porsche wheel hub assembly tolerance is /-0.05mm (concentricity and parallelism, from factory of course). I know… hard to believe. Go ask them they’ll confirm that with pride (it’s a Porsche you have Sir!).

So when your friend Markus tells you, no paint, no dirt, get rid of the rust, etc… he is NOT joking. If they are not installed ‘permanently’ flat then both the wheel and your safety will soon be compromised. Although I don’t see Woody’s silicon being the main culprit in his little adventure. I mean look at the spacer; no hub support (floating?!), open PCD, and possibly the wrong alloy, silicon or not my guess is they would eventually have brought in trouble (Asia rocks for other things, not Porsche spacers!).

So when you’ll be out to score wheel spacers, buy them from those who knows what they are doing lolll H&R in Germany for instance, they are two others that I know who also machine theirs within TOL and uses the correct 7075 alloy mix. No comments for the rest of the manufacturers… we’ve actually seen quite a few actually. Illegal s h i t e I tell ya lollll

RE materials; we have to import ours from Austria here as the local 7075’hardness is literally near the same as the 6061 grades anodized/heat treated or not. No Go for “performance” spacers. The local stuff simply deforms & compresses. Use local grades alloy and you’ll have to re-torque your wheels every bloody weeks simple as that.

So… you see. Nothing is simple :/ You’d think a spacer is just a silly dumb plate and bahh it’ll work man. Possibly just fine for cruising down the neighborhood, going to buy some milk at the store etc (I actually agree) but the reality is its not always like that, one day you’ll need to maneuver that Porsche car and its at that moment that you and your passenger will appreciate your properly engineered and machined spacers.

Keep away from Asian spacers (please, folks)."

-Kevin