The long-awaited platinum and palladium exchange traded funds (ETFs) have already seen so much interest that they may soon reach their position limits. In their first few days of trading, hundreds of thousands of shares changed hands.

Although the first physically backed platinum and palladium ETFs were just released last week, they’re already seeing major interest. ETFS Platinum Trust (NYSEArca: PPLT) and ETFS Palladium Trust (NYSEArca: PALL) hold physical bullion of their namesake metals. [More on the funds’ debut.]

More than 414,000 shares of PPLT and almost 295,000 shares of PALL exchanged hands since launching, and assets in the funds may see quick growth, explains Laura Crigger for Index Universe.

There are strict share limits that are controlling how large the ETFs can grow, however. According to the funds’ prospectuses, PPLT is limited to holding 478,000 ounces of platinum, which, at Friday’s prices, translates into approximately $751 million in assets. [Why are precious metals ETFs rallying now?]

The ETFs do have some way to go before they are maxed out, however, at the rate they are growing, it should happen sooner than later. ETF Securities put the caps in place to alleviate concerns that the two ETFs could create a shortage in the physical metals, which are widely used in a variety of industrial applications. Those concerns exist because the markets for platinum and palladium are much smaller than those of other precious metals, such as gold.

If the ETFs actually do hit these limits, it’s not certain what would happen. The funds could trade at a premium to their net asset value (NAV), which could send platinum investors back to exchange traded notes (ETNs) that track platinum. ETF Securities could also ask the Securities and Exchange Commission (SEC) to remove the limits, but whether they would or how quickly they could is a question mark.

For more stories about platinum, visit our platinum category.

The opinions and forecasts expressed herein are solely those of Tom Lydon, 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.