Replacement handle for brass portafilter. If you don't have the right tools these can be difficult to replace.
These handle are an improvement over the older square handles, being quite a bit thicker and sturdier. They do not fit the aluminum portafilters.
You will need a 10mm nut driver or thinwall socket (regular socket is too large). In addition, there is a possibility of breaking the old bolt during removal, so use proper technique in removal (liquid wrench or heating the handle with a torch, etc).