The source (QuantConnect Strategy Library 'Momentum Effect in Stocks', after Quantpedia / Jegadeesh-Titman) ranks the 50 largest US stocks by 12-month price change and holds the leaders equally weighted, rebalancing monthly. We keep the mechanism (12-month cross-sectional momentum, equal weight, monthly rebalance, long-only) and change the universe to one the factory can run and that is not a hand-picked list. A 50-stock top-market-cap universe runs into lessons L173 (top-N baskets of 20-60 names time out after 3 iterations) and L151 (a list of today's mega caps carries survivorship bias; we have no point-in-time market-cap data). Instead the universe is the complete set of Select Sector SPDR ETFs: XLB, XLE, XLF, XLI, XLK, XLP, XLU, XLV and XLY, all listed since Dec 1998, plus XLRE (from Oct 2015) and XLC (from Jun 2018). The list is fixed by the GICS sector classification, not by knowing which names did well. It is point-in-time: an ETF is eligible only once it has 252 daily bars of history. That caps the book at 11 names, and there is 27 years of daily history. Momentum is the 12-1 return, close(t-21)/close(t-252) - 1, skipping the latest month to avoid 1-month reversal; the source's raw 12-month change is pre-registered as variant B. On the first trading session of each month, rank the eligible sectors and hold the top 3 at equal weight (1/3 of equity each, 1x, no margin). A sector's slot goes to cash if its own 12-1 return is below 0 (absolute momentum). That is the flat state: expected ~15-20% of months partly or fully in cash, and ~10% fully flat (2001-02, 2008, 2022 H1). Portfolio-bucket rationale: USEQ is 2.5% of the corpus, sector ETFs are archetype #1 in the equity brief, and nothing in the pipeline is a US sector-ETF rotation. SPY is deliberately not used as a signal or hedge leg (no signal-on-A/trade-B, no neutral book). Source credit: QuantConnect Tutorials, 04 Strategy Library / 21 Momentum Effect in Stocks, sections 'Momentum Calculation' and 'Monthly Rebalance'.