The Flashforge dreamer is a great printer, but the internal spool holders don't work well with non-FF spools. These replace the side 'windows' with 3D printed spool holders.
I've installed these on 2 printers, on one I had to use the clip (drilled a small hole on the back and screwed it in, and on the other it was a snug fit so it wasn't necessary.
The shims raise the cover so that you can feed the filament through the small opening between the lid and the body of the printer.
Printed these with ABS at 230 C extruder, 105 C bed, 4800 mm/min.