I believe the HiFi is a TO4B so it's smaller. Also, I'm almost positive a .63 is a T3 size housing. The T4 is .68 or .70 I can't remember which.
I believe the HiFi is a TO4B so it's smaller. Also, I'm almost positive a .63 is a T3 size housing. The T4 is .68 or .70 I can't remember which.