I had time to un-box and inspect the Vertex media reactors.
My initial reaction is that of disappointment.
Both units were received from BRS having been opened with the seals broken
The top O-ring on one unit is damaged, the O-ring on the other unit was badly twisted.
Although difficult to see in the photo, the section where the downtube and O-ring mates with the top-lid is badly scarred which, if left unpolished, I imaging would quickly destroy the O-ring.
One unit was supplied with a spare main O-ring (seen in the bottom of the right unit) whereas the other contained no spare.
My greatest disappointment is the overall design of the unit. I was willing to pay a premium for these as I had hoped they would provide the simplest/fastest cleaning and media replacement. The downtube O-ring has to be engaged 4 times for each cleaning and media replacement as both the top lid and top diffuser plate must be removed over the very tight-fitting O-ring on the downtube. It's very tedious to do. Based on the fact one O-ring was received damaged and the other twisted - Even with proper lubrication, it will seemingly result in a very short life and far too-frequent O-ring replacement.
I'll reach out to BRS and see how they and Vertex will handle the issues before determining if I keep these, or return them and choose alternate reactors.