Your camera has a T-Thread at the front and you want to load an IR or CLS filter to it. By using the ZWO-T2-1.25 3mm adapter you screw it into the T-Thread on the camera and the 1.25″ filter into the adapter. Leaving you enough T-Thread to load it onto your scope.
Name: T2-1.25″ Filter adapter
Thread: outer M42*0.75 male thread, inner M28.5*0.6 female thread