5e SRD:Ball Bearings (bag of 1,000)
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Ball Bearings. As an action, you can spill these tiny metal balls from their pouch to cover a level, square area that is 10 feet on a side. A creature moving across the covered area must succeed on a DC 10 Dexterity saving throw or fall prone. A creature moving through the area at half speed doesn't need to make the save.
Cost: 1 gp
Weight: 2 lb.