There are two stainless 5/16 fender washers behind the rubber mount & one in front, each of those washers are.055 which total .165. Wards says that there should be at least 1/4" of space between the fans & heads & mine are about 5/16". The reason I did it that way is because there are enough extra threads on the back of the rubber mount that .110 of spacer could be used but no more & the .055 on the front still left plenty of stud for securing the fan itself. The hex nut spacer is made to extend all of the way into the mounting hole of the fan & this gives enough material to have a 5/16-18 stud with red loctite installed so that the original horn nut could be used. I hope this helps but if there are any more questions don't hesitate to ask. One more thing, the rubber mount is the stock mount & the hex spacer is threaded all the way through & is used to secure the fans & have the stud for the eagle head & horn to be secured.