Just a way to support two 30mm fans on double hotends without limiting to the type of hotends (should work for most types). You should use BIG zip ties in order to fix it. It is open, meaning it does not enclose the hotends for better ventilation, but depending on the design of your printer that? could also mean that it throws a lot of air on an ABS print, which is undesirable for it might cause warp. BOM: You should press the M3 nuts in their cavities (don't forget to activate XY/horizontal compensation if your slicer have it so that the holes don't become too tight) then attach the fans by inserting the screws. Since it becomes so steady, you don't even have to use all screws - if you notice the pictures, I don't. Then just hold it to your double hotend then insert the zip ties into the lateral tabs.