TWSBI Diamond 580RBT Fountain Pen - Red / Blue / TransparentThe lightest of the Diamond 580 pens The TWSBI Diamond 580 is the original expression of the Diamond series, built around a traditional piston filler and a full demonstrator design that puts the internal mechanics on display. With a clear view of ink movement and the filling system, it brings you closer to the act of writing itself. This model reflects the foundation of TWSBIs design philosophy, with a lighter construction than the AL and ALR