These may fit a little weird as the thread pitch/height is different than the standard F_239. With Rancilio portafilters, they always come to rest slightly to the right when tightened down all the way in a bench vice.
This part can be challenging for some to install. Many times the thickness of chrome on either this spout or the threads on the portafilter (or both), varies, and getting the spout to thread on may require more than one attempt. If it will not install far enough, a wrench and a very strong twist should position it over. In some extreme cases the only option is to clamp the spout in a bench vice and crank the handle onto it. If it threads on too far PTFE plumbers tape or a gasket may be required.
Attention CA Residents: Prop 65 Warning
WARNING: This product can expose you to chemicals including lead, which are known to the State of California to cause cancer, birth defects, or other reproductive harm. For more information, go to www.p65warnings.ca.gov.