ready in 1 hr 35 min.
In a kettle, combine pears and plums. Stir in pectin.
Bring to full rolling boil over high heat, stirring constantly. Stir in sugar; return to a full rolling boil. Boil for 1 minute, stirring constantly. Remove from the heat; skim off foam.
Pour into jars and cool to room temperature, about 1 hour. Cover and let stand overnight or until set, and then refrigerate.