Lanxivi 30 PCS Jinhao Fountain Pen Cartridge for Jinhao ,Duke ,Fuliwen and Baoer Pen Standard Size (Black Color) Lenght : Appr 51mm , Cartridge Diameter : Appr4-6mm, Bore diameter : 2.6mm Fit standard Fountain Pen such as Jinhao ,Duke , Baoer, Hero and 98% of Chinese fountain pen Package : 30 PCS fountain pen cartridges black color Not Fit The LAMY and PARKER Fountain Pen 100% Satisfaction Guaranteed : If there is any reason you do not like the pen ,just send us a message ,we can offer you a full refund or replacement !