The VanEck Vectors Oil Service ETF (NYSEArca: OIH) is largest oil services ETF and is cap-weighted fund, dominated by the industry’s largest companies.

Rivals to OIH and XES include the iShares U.S. Oil Equipment & Services ETF (NYSEArca: IEZ) and the PowerShares Dyanmic Oil & Gas Services Portfolio (NYSEArca: PXJ).

Both XES and IEZ track a slightly broader 37 components, but XES follows a more equal-weight indexing methodology that favors midsized companies while IEZ reflects a traditional market cap-weighted indexing methodology. Lastly, PXJ follows a fundamentally weighted index, which selects stocks based on price momentum, earnings momentum, quality, management action, and value.

“But most energy stocks tend to follow the price of oil more closely than profits. The ETF’s performance has shown a close correlation to oil prices for at least the past three years. On that front, the price of oil has stalled since June, and forecasts are uncertain,” reports IBD.

For more information on the crude oil market, visit our oil category.