It is one of the issuers first actively-managed, non-transparent ETFs. Selection is based on individual company analysis, rather than broad economic forecasts. The portfolio generally holds 20-40 US midcaps with long-term growth and positive ESG traits. Firms are also gauged based on the UN Sustainable Development Goals (SDG) which may include: quality education, gender equality, and responsible consumption and production. The portfolio managers create an impact thesis to explain the firms SDG alignment along with its fundamental growth. Unlike other ETFs that publish full portfolio holdings daily, MID publishes a proxy portfolio on its website. It only includes some holdings, designed to track MIDs daily performance and help facilitate arbitrage opportunities. Holdings are disclosed on a quarterly basis, with a 60-day lag.