It seems Blue Robotics have changed their thruster design since piercet's original intake grill was designed (or it was actually only good for the T100?) - the motor now sticks out about 13mm on the front, leaving a gap when using the intake grill.
These are 2 parts that allow filling that gap and mounting the whole lot to piercet's mount with proper spacing.
Note the 2 holes for the read guard are a bit (about 1mm) too close to the main thruster holes on the mount, but enlarging the holes a bit with a drill makes things fit (that's why the square rest ends up not lining up well to the rear grill, it's been aligned to the mount...)
Full for ring, 30% for spacer