Cragar Mach 8 Spacers

Dude, those look sketchy to start! Looks like they were cast in someone's sand box. How do they work, is the OD of the casting the ID of the lug hole or are they just spacers held in a circle? back look like these? just a normal spacer but it looks like they are unilug so the crescent spacer may locate the lugs...?

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I think they press into the back of the wheel. I know they said you can't mount the wheels without one of the spacers in there. Dad had 4 wider spaces that they used and that located the rear wheels fine but the fronts look stupid. I don't have a picture of the back of the wheel, but my brother is going down there this weekend to visit and take Dad to a car show. I'll have him zip a wheel off and snap a pic of what the back looks like so I can post it.