RWK's revenue-weighting scheme provides a stark alternative to vanilla mid-cap coverage. It applies revenue-weighting to the S&P mid-cap 400. Specifically, each constituent security is weighted based on the sum of the companys revenues for the trailing four quarters, subject to a maximum 5% per company weighting. The Underlying Index is rebalanced quarterly. Prior to June 4, 2018 the funds underlying index was called OFI Revenue Weighted Mid Cap Index. After the market close on May 24, 2019, the Oppenheimer S&P mid-cap 400 Revenue ETF was reorganized into RWK.