This Esterbrook ReNew replacement nib and feed unit is marked 2550, a Firm Extra Fine nib made of stainless steel. Esterbrook ReNew nib units are interchangeable, and to change them, you simply unscrew one and screw in another one.
This thing writes well and writes extremely fine. One of the best EFs I have used. I wish that modern pens offered anything close to the quality and value of the options that Esterbrook did more than half a century ago. Esterbrook is amazing.
This is the best nib I have found. Great for fine writing style
