# Owl Mastery > Free daily gamma exposure (GEX) levels, signals and key stats for US stocks and indexes, updated after each market close. Prices, signals and gamma levels update once a day, after the US market close. Free without an account: price, key stats, performance, four signals (RSI, distance from the 50-day average, 20-day volatility and distance from the 52-week high), and the daily HVL, call resistance, put support, gamma wall and one-day range. With a free account: exposure by strike, front-expiry levels, top strikes, chart ranges, ticker lists and a portfolio. ## Stocks - [Stocks](https://owlmastery.com/stocks): Daily gamma levels, close and change for every US stock and index Owl Mastery covers. - [SPX](https://owlmastery.com/stocks/SPX): S&P 500 Index - [NDX](https://owlmastery.com/stocks/NDX): Nasdaq-100 Index - [RUT](https://owlmastery.com/stocks/RUT): Russell 2000 Index - [VIX](https://owlmastery.com/stocks/VIX): Volatility Index - Each covered ticker has a page at https://owlmastery.com/stocks/{SYMBOL}, for example https://owlmastery.com/stocks/AAPL. ## Learn - [Learn](https://owlmastery.com/learn): A glossary of gamma exposure and trading signal terms, and an explainer for each. - [50-day moving average explained](https://owlmastery.com/learn/50-day-moving-average): The 50-day moving average is the mean of the last 50 daily closing prices, recalculated each day as the newest close enters and the oldest drops out. It gives a guide to the medium-term trend, since a close above it is higher than the average close of roughly the last ten weeks of trading. Owl Mastery shows how far each close sits from its 50-day average, in percent. - [Call wall and put wall explained](https://owlmastery.com/learn/call-wall-put-wall): Call wall and put wall are common names for the strikes where call or put options positioning is largest. On Owl Mastery, call resistance (call wall) is the strike with the largest net gamma exposure. Put support (put wall) is the strike with the most negative net gamma exposure. Other sites may define their walls by call-only or put-only gamma or by open interest, so their strikes can differ. - [Distance from the 52-week high explained](https://owlmastery.com/learn/52-week-high): Distance from the 52-week high is how far the latest close sits below the highest price of the past year, in percent. A reading near zero means price is close to its high for the year, and a large negative reading means it has fallen well below it. Owl Mastery computes it as the close divided by the highest high of the last 252 daily bars, minus 1, times 100. - [How to read gamma levels on a chart](https://owlmastery.com/learn/how-to-read-gamma-levels): Check the date of the levels, then whether the close is above or below the HVL. Hedging may damp moves above the HVL and add to them below it. Call resistance marks the strike with the largest positive net gamma exposure, and put support marks the strike with the most negative net gamma exposure. The one-day range is the move priced in by implied volatility for one day. Treat each level as a place where hedging flows may change, not a price that has to hold. - [HVL, gamma flip and zero gamma compared](https://owlmastery.com/learn/hvl-gamma-flip-zero-gamma): Owl Mastery's HVL (high volatility level) is found by adding net gamma exposure from the lowest strike upward. The HVL is the strike where that running total reaches its lowest point. Net exposure is negative on balance below the HVL and positive on balance above it. Other sites publish gamma flip or zero gamma levels for a similar boundary, but they may calculate them differently, so the numbers need not match. - [Positive vs negative gamma and dealer hedging](https://owlmastery.com/learn/positive-vs-negative-gamma): Positive and negative gamma describe how options dealers' hedging may react to a price move. When dealers are long gamma, they tend to sell into rallies and buy into dips, which may damp moves. When they are short gamma, they tend to buy as price rises and sell as it falls, which may make moves larger. - [What is gamma exposure (GEX)?](https://owlmastery.com/learn/gamma-exposure): Gamma exposure (GEX) estimates the dollar value of the underlying that options dealers may need to buy or sell for each $1 move to maintain their hedges. Owl Mastery calculates it strike by strike from that day's options open interest, counting calls as positive and puts as negative. Positive net GEX may accompany calmer, range-bound trading, while negative net GEX may accompany larger, faster moves. - [What is historical volatility and how is it annualized?](https://owlmastery.com/learn/historical-volatility): Historical volatility, also called realized volatility, measures how much a price actually moved over a past window. It is the standard deviation of daily returns, scaled to a year by the square root of the number of trading days, which is 252 for US stocks and usually 365 for crypto. Owl Mastery's Volatility (20D) is the sample standard deviation of the last 20 daily log returns, times the square root of 252, times 100. - [What is RSI? Relative strength index explained](https://owlmastery.com/learn/rsi): The relative strength index (RSI) is a momentum indicator that compares the size of recent gains with the size of recent losses on a scale from 0 to 100. J. Welles Wilder Jr. introduced it in 1978 with a 14-period setting, and readings of 70 or more are commonly called overbought and 30 or less oversold. Owl Mastery computes Wilder's RSI over 14 daily closes for every US stock and index it covers. - [What is the expected move? The implied one-day range](https://owlmastery.com/learn/expected-move): The expected move is the price range implied by option prices for a period, usually one standard deviation on either side of the current price. Owl Mastery's one-day range is spot plus or minus spot times IV30 divided by the square root of 252. IV30 is the implied volatility of the listed expiry closest to 30 trading days out. Under a normal model, the next close lands outside a one-standard-deviation range on roughly one day in three. - [What is the gamma wall?](https://owlmastery.com/learn/gamma-wall): On Owl Mastery, the gamma wall and call resistance are the same strike by construction. The gamma wall marks where net options gamma is most concentrated. It is the strike with the largest gamma times open interest, with puts counted as negative, computed over every strike after each US close. Owl Mastery shows both names in one row of the levels table. Other providers may compute a gamma wall differently. ## Methodology and policies - [Methodology](https://owlmastery.com/methodology): How each level and signal is computed, when the data updates, and its limits. - [About](https://owlmastery.com/about): What Owl Mastery is and who it is for. - [Disclaimer](https://owlmastery.com/disclaimer): Owl Mastery publishes market information, not investment advice. ## Optional - [Privacy](https://owlmastery.com/privacy): What Owl Mastery stores and why. - [Terms](https://owlmastery.com/terms): The terms for using Owl Mastery.