Golden Airbrush Transparent Extender - now known as High Flow Medium contains lower levels of retarders compared to Airbrush Medium.
While Airbrush Medium will thin acrylic colour, when a high ratio of Airbrush Medium is required to mix with small ratios of colour (creating tints perhaps) the level of retarders can detrimentally affect drying. High Flow Medium can be added instead.
High Flow Medium can also be used to precisely control the transparency of colour.
NOTE: This product may be labelled as High Flow Medium or as Airbrush Extender - it is the same product