It has been a tough week for an exchange traded fund (ETFs) that lets investors short silver as trading volume in the product has surged along with metal prices.

ProShares UltraShort Silver (NYSEArca: ZSL) was down more than 5% Thursday afternoon on heavy volume as silver traded above $46 an ounce to levels not seen in over three decades.

Nearly 12 million shares of the bearish ETF traded Thursday in afternoon action. On Wednesday, more than 15 million shares traded, while the average daily volume is around 3 million shares.

The furious rally in silver prices has been brutal on the ETF, which allows investors to bet against the metal or hedge existing positions.

ProShares UltraShort Silver is programmed to produce daily returns that correspond to 200% of the inverse performance of silver bullion. It is down more than 40% over the past month, according to Morningstar, although the ETF is designed as more of a trading tool than a long-term holding.

ProShares UltraShort Silver

The opinions and forecasts expressed herein are solely those of John Spence, and may not actually come to pass. Information on this site should not be used or construed as an offer to sell, a solicitation of an offer to buy, or a recommendation for any product.