NEMA 17 (42mm x 47mm) stepper motor cooler. Suits 40mm x 40mm x 10mm fan.

thingiverse

To prevent blowing onto the printer bed, use both the left and right exhaust. Print with ABS and ensure at least 70% infill for stability; this prevents warping. Fans fit tightly without needing screws; if clicking, sand slightly. Update 1 includes cable management and zip-tie holes, while update 2 offers a "twin fan" version to cool the head, addressing heat issues when printing enclosed ABS that may cause layer softening and jamming due to rapid heating of the nozzle.