Install the E3D V6 hot end on your Ultimaker 2 or 2+ printer.

It is equipped with a dual airflow design and can be fitted with a 30-mm fan. The fan has a height of 5 mm, which effectively avoids the fixed clamp of the heating bed.
I used a small self-tapping screw to fix the fan.
The axial distance between the shafts of the LM6LUU bearing is 18 mm

Update: On April 7, 2019, the STEP file of reximes has been uploaded