The most common rollerball refill shape used in the world is the ‘Schmidt 5888”. These brands accept the ‘5888’: 5280, Aurora, Conklin, Diplomat, Esterbrook, LeBOEUF, Faber – Castell, Marlin, Monteverde, Otto Hutt, Padrino, Pineider, Pininfarina, Porsche Design, Rotring, Schmidt, Sheaffer, Visconti, Waterford and more….