Gold is one of this year's best performing commodities and that's a theme that could extend as exchange traded fund demand swells and as central banks debase currencies.

That's good news for gold miners ETFs, which are already among 2020's leading industry funds. The VanEck Vectors Gold Miners ETF (NYSE:GDX), the largest fund in the category, is rewarding investors taking a chance on what's usually a volatile product. The fund is higher by nearly 23% year to date.

GDX and its small-cap counterpart — the VanEck Vectors Junior Gold Miners ETF (NYSE:GDXJ) — have a way of crowding out the other ETFs in this group, but some of the other undiscovered funds here are turning in great performances in their own rights.

With that in mind, here are some hidden gems of the gold miners ETF space to consider.

Sprott Gold Miners ETF (SGDM)

The Sprott Gold Miners ETF (NYSE:SGDM), which has recently been making a series of all-time highs, is an odd choice for an overlooked because it's neither small nor young. Just a couple of months shy of its sixth birthday, SGDM has $240.5 million in assets under management.

The fund is a departure from cap-weighted rivals such as GDX. SGDM follows the Solactive Gold Miners Custom Factors Index, which focuses on “larger-sized gold companies with the highest revenue growth, free cash flow yield and the lowest long-term debt to equity,” according to the issuer.

Low debt, well-capitalized firms, regardless of industry, are rewarding investors this year and that's true in the precious metals mining space as SGDM is higher by 24% year to date.

U.S. Global GO GOLD and Precious Metal Miners ETF (GOAU)

The U.S. Global GO GOLD and Precious Metal Miners ETF (NYSE:GOAU) is truly unique among its gold mining ETF rivals because it blends exposure to production firms with royalty operators, which are passive participants in the industry. Royalty and streaming companies comprise about a third of GOAU's index.

The fund follows the U.S. Global GO GOLD and Precious Metal Miners Index, which is rooted in quantitative analysis.

There are some perks to the royalty exposure including reduced volatility, higher dividends and lower operating costs. GOAU is higher by almost 29% over the past month.

Global X Gold Explorers ETF (GOEX)

At nearly 10 years old, the Global X Gold Explorers ETF (NYSE:GOEX) is one of the oldest products in this category and it's experiencing a renaissance this year as confirmed by a 27.49% surge over the past month.

GOEX components have a weighted average market value of $1.98 billion, making this a small-cap play on gold explorers. That's a volatile combination, but it's one that can pay off if both gold and smaller stocks remain simultaneously remain firm.