The portafilter spring is a part that sits inside the portafilter head and keeps the filter basket in place. It's not a part you think about much until you lose or damage it. You quickly realise how hard they are to find. Thankfully, if you're reading this page, you've solved that problem. Buy a replacement and give your 58mm espresso portafilter new life and new utility with this replacement spring which is made of stainless steel and is 1.2mm in thickness.