The fund tracks an index that measures the performance of the December WTI light sweet crude oil futures contract. The fund expects positive gains during the winter months by only investing in December contracts of each year, which is often the most liquid. As the oil market is typically in a state of contango, near-month contracts create constantly changing underlying investment, which can prevent accurate tracking. By investing only in December contracts, the fund eliminates the monthly futures contract roll which often creates negative roll yield.