Bitters to taste (I use a combination of Angostura and Orange bitters)
Place one slice of lime in each popsicle mold. Mix grapefruit juice, Aperol and bitters in a small pitcher and pour into the molds. Place the cover on the molds and insert popsicle sticks.
Freeze for four hours or overnight.
To unmold, remove the mold from the freezer and run a butter knife under the cover to release the lid. The corners can be a little sticky. Pull the individual popsicles out of the mold. You can remove the ice pops from the mold, place them in a ziplock bag and return to the freezer to store until you are ready to serve them.