Potion of Diminution

From Dungeon Master's Guide, page 187. Found on Magic Item Table C.

Description
''Potion, uncommon. 0.5 lbs.''

When you drink this potion, you gain the "reduce" effect of the Enlarge/Reduce spell for 1d4 hours (no concentration required). The red in the potion's liquid continuously contracts to a tiny bead and then expands to color the clear liquid around it. Shaking the bottle fails to interrupt this process.