sorry man, I never got the message until today, do you still need. I think it's about 4", but I'm not home right now and can't tell.
As to those saying it was over tightened...simply put, no. I'm not new at audio/video stuff and installed it for years pro. I was a DJ at the age of 12, yes 12. And spent a lifetime around audio. I do not overtighten things. This thing simply failed.