I bought a new steam valve as well as the old one went stiff and broke the original knob reviewed. It lasted 5 years. Turned out the valve was easy to fix..... . The spring shown is the nub of the matter. Without it, the knob stem will break. So ensure its properly installed - not difficult. The plastic is essentially a filler. The part is not really up to the job, long term, but no realistic alternative exists. I could make something better but life is too short.