The invention provides a perfusion stock composition, for preserving a donor organ for transplantation, comprising: a source of 60 to 100 mM Na+; a source of 10 to 20 mM K+; a source of 5 to 10 mM Mg2+; a source of 0. The thin, flat and extended nature of the flexible tape heater may enhance heat transfer with the gas flow whilst also providing low impedance to the gas flow. A transport arrangement handles lenses during hard coating in a dip trough.