Hi, On my super duper LD32 engine, I'm fitting an RB flywheel and clutch. I've been measuring it up and comparing to a standard 240mm flywheel and clutch, and it's about 9mm taller in aggregate. I know there are a number of different height clutch collars around, but I don't know their heights. I've got this one spare, which I think is the original 260z one my car came with mated to a 225mm flywheel. its about 23mm between the two contact surfaces. and I've got the one in the car, that I got from MrF to go with my 240mm flywheel. I don't know how big it is, cos it's in the car! If you've got any clutch collars around to be measured, I'd be very grateful if you could measure the distance between those two contact surfaces and let me know.