S3 - KO4 Turbo inlet dimension?

I've been searching for quite some while, trying to find what size silicone coupler I need to come of the turbo for my CAI. I think it's 51mm off the turbo?
But measuring the oem pipe that came off it seems larger? Anyone any idea.

Yeah the internal diameter of the OEM pipe is of course the right size, it's just such an a*se to measure as it's soft convoluted rubber. Using my vernier it measures 56-58mm diameter with the hose clip off. What threw me was the fact that when searching the web I keep seeing refs to 51mm diameter. So wondered if anyone had the 'official' dimensions. Or had replaced their silicone coupler on their CAI so knew what size to get.
In short i'm going to be best to take my existing silicone coupler off and measure it.