Thread Size of Spikes for Revel F206


Was hoping that someone might know the thread size for the floor spikes. Bought a pair of used F206s that came without the floor spikes. I am looking to put on a pair of outriggers and need to find the right size bolt.

I found somewhere on internet that it was 1/4"-20 but this is way too small. A 5/16"-16 is close. I can get a couple of threads on and then it binds up.

Any help would be appreciated !
cobes987
Thanks for your replies everyone. Sorry, I did mean 5/16-18.

After a few trips to home depot I figured out the correct size. It is indeed metric !

For anyone that comes across this problem in the future the hex bolt is 8mm diameter with 1.25 thread size (M8-1.25)

Theo: I like the Revels quite a bit but don't have a lot of experience with different speakers or the previous Revel Performa series. I bought them based on reviews alone and have not been disappointed.
Cobes, thank you for your response. I would agree that if they are reviewed to sound better than the previous models, I couldn't go wrong. I am hoping there will be some on display at RMAF this year.