This is easy-to-print and efficient remix from BMG Duty 1st gen for  Ender 3 / CR-10 printers.
This remix features the ability to use with a stock 34mm stepper motor and the ability to hotswap e3dv6 and volcano extruders.
You can use the original fan duct and the ones uploaded here.
The original ducts have the ability to adjust the position relative to the nozzle.
The uploaded ones are distinguished by the use of the m4 bolt for mounting the fan and only two positions - the upper one for the e3dv6 and the lower one for the volcano. This saves you from having to adjust the position of the ducts.
UPDATE 06.05.2021
Reduced the size of the slots for the radiator mounting nuts;
2 x 22 mm bolt M3 is replaced with a 2 x 25 mm bolt M3;
2 x 27 mm bolt M3 is replaced with a 2 x 30 mm bolt M3.