We sell a few different models of 3D printed adapters to connect 120mm fans to ventilation systems. These devices are primarily intended to be used to exhaust heat from crypto mining machines to the outside, but can be attached to almost any device with a 120mm fan. For the time being we only sell these on our eBay store, but other purchase options will be added soon.
For ventilating individual 120mm fans we sell two different models, one that can mount the fans to 4in ducts and one for 5in ducts. Please note that due to interference issues it is not possible to attach two 5in mounts to a mining machine with two adjacent exhaust fans such as the Antminer S19. For this situation we are developing a single mount for these larger mining machines that allows for mounting to a 6in duct, but two of the 4in mounts will work in this situation.