The Bollinger Bands were developed by John Bollinger and are primarily used for presenting the volatility of the stock in an easy to view form. By definition prices are high at the upper band and low at the lower band. Bollinger Bands consist of a set of three curves drawn in relation to the stock price. The middle band is a Simple Moving Average (SMA) used to measure of the intermediate-term trend that serves as the base for the upper band and lower band. The interval between the upper and lower bands and the middle band is determined by volatility, typically the standard deviation of the same data that were used for the average. The default parameters are 20 periods and two Standard Deviations.