I don't have that adapter (the bit under the red arrow). It looks like it will do what it says,
"Allows connection with a 27mm hose. (Will directly connect with Festool brand 27mm hose.)"
I do have the Mirka hose. Bought it from
Supergrit for $45. The hose included the rubber ribbed tool connector (the part to the left of the red arrow) so it is a good value in my book. The fact that the tool connector is included is never mentioned and never shown in the listings (any listing that I've seen) so call Supergrit and make sure if you order.
The Mirka connector is a little different than the Festool connector. The Festool connector locks onto the hose and it takes a screwdriver to separate because the swivel joint is at that connection. The Mirka connector screws right on to the hose by hand very quickly. The swivel is between the thread and the ribbed rubber tool connection. Also, the rubber on the Mirka version is a little softer than the Festool version which makes it easier to fit to the oval shaped ports on some Festools.
If I'll be using the Ceros on a project I just keep the Mirka hose connected to the vac and use the tool connector with Festool tools. When I want to use the Ceros sander I just unscrew the rubber connector from the hose and screw it onto the sander. Takes about as long to do it as it does to write these two sentences.
The Mirka hose itself is also a little different from the Festool hoses. A Mirka employee told me it is anti-static (another thing not mentioned anywhere) but in use the Festool hoses are more anti-static.
The Mirka hose plastic more closely resembles Miele hoses but the Mirka is tapered. At the business end it is 25mm, slightly less than the standard Festool hose, but at the vac end it is about 32mm. I can easily imagine an engineer arguing that the tapered hose is superior somehow.
It is also a little stiffer than the Festool hose. You can't get it into a Systainer but it holds a fairer curve than the more easily bendable hose and all in all it's probably just as efficient. I use it with the circular saw with no complaint.