The reducer helps to facilitate a connection between 1/4 IPS female threaded parts and 1/8 IPS male threaded parts. This part is designed so you can reduce the size of fittings from 1/4 to 1/8 IPS. In order to do this, you would need to use a 1/4 IPS coupler as well. Then you would connect the 1/4 tubing to the coupler, then the coupler this reducer, and finally the reducer to the 1/8 tubing.