Belt sprocket with 5M-15 pitch. This belt sprocket can be used on any motor application that uses a 3/8 D-shaped shaft.
Belt sprockets are usually designated by the pitch (distance between cogs) plus number of cogs (or teeth). For instance, an M5-15 belt sprocket has 15 cogs around the axis, each cog being 5 mm distance between it and its nearest neighbors on either side.