2. Market Vectors Oil Service ETF ( OIH) seeks to replicate the price and yield performance of the Market Vectors US Listed Oil Services 25 Index. The Index is comprised of common stocks and depository receipts of US exchange-listed companies of oil services sector. Top holdings include Schlumberger Ltd ( SLB), National Oilwell Varco Inc ( NOV), and Halliburton Co ( HAL). In January, the fund gained 10.4%. The expense ratio is 0.35%.