The position of the proprietary advocates argues that manufacturers are entitled to sell their own accessories for their products, and that standard formats can lead to quality problems. Counter-positions see proprietary cartridges as a declaration of war on the customer that unnecessarily restricts the choice of ink; piston fillers or converter systems that allow free choice of ink are therefore preferred. A pragmatic stopgap was formerly the refilling of empty cartridges with syringe and cannula, as was usual e.g. with Geha pens.