TWSBI Eco Fountain Pen - Plum with Onyx Trim and NibA plum Eco that shifts depending on ink choice The TWSBI Eco Plum is a piston filling fountain pen with a deep crimson body and subtle black trim. The transparent barrel means the overall appearance shifts depending on the ink inside, moving between warmer red and cooler pink tones depending on what you fill it with. It remains a practical Eco at its core, with the same high ink capacity and reliable piston mechanism. What sets it apart High capacity