what size trach is this?

I have a patient with a trach that was put in at another hospital. One side says 6.0 ID, 8.8 OID, 70 L, and mm. The other side says Portex Bivona TTS 11 mm. I am assuming this is a size 11 trach, but the Portex website does not have a size 11 listed. Most sizes are between 6 and 9, that I can find anywhere. Am I looking at the wrong number?
Bivona� Adult TTSThis is what it is based on the information provided.Reorder Code 670160It's a 6mm Inside Diameter Trach.

You might find this helpful. It explains what the measurements mean. http://services.aarc.org/source/Down...04.05.0497.pdf