CNC-machined from 1/4" poly sheet, and grooved for neoprene o-rings on both sides. The BEST you can get. Won't leak, won't crush, won't wear out. SOLD EACH.
To replace Ducati part number 0755-92-570, the rubber insulator used with later SPIGOTED manifold, as shown in 2nd photo. To suit 30 or 32mm carb of roundcase twin and early squarecase, I believe.
ID of spacer 34mm, stud spacing 52mm c-c, if interested in other applications.
I will answer questions promptly, good luck and thanks for looking.