This is a small plant (note the canister or cup from which it is hanging for the photograph session). Its serrated or “tooth-like” leaf margins are the source of its name. A close-up of the flowers give a better idea of their true color.
The Stewarts grow many of the unifoliate (single-leaf) streptocarpus like this — affixed to a piece of tree fern of the sort used for mounting some epiphytic orchids, with long-fiber sphagnum moss at the base to allow for some root spread. This mimics the epiphytic (tree growing) or lithophytic (rock growing) habit of many of these species in nature. It does require greenhouse or lathe-house conditions, as watering involves essentially wetting down the tree fern plaque and moss, guaranteed to then drip onto the floor.