Abstract: In a spare bottle for an ink refilling of piston-type fountain pens or of writing implements fitted with an ink reservoir and an ink conducting system, in which refilling container (10) is provided with an attachment (13) having a substantially cylindrical docking section for the fluid-tight accommodation of a connecting piece to a refillable writing fluid chamber, more particularly for the accommodation of a terminal section of a piston-type fountain pen (14) facing the nib or a refillable ink cartridge (15) and can be closed by means of a cap portion (12) with the aid of a screwed, plugged or clipped connection, the docking section (13) further possessing a sealing collar for engaging into the neck of the refilling container (10), which is comprised of soft, elastic plastic.