In trading on Friday, shares of the Silver Miners ETF ( SIL) entered into oversold territory, changing hands as low as $34.90 per share. We define oversold territory using the Relative Strength Index, or RSI, which is a technical analysis indicator used to measure momentum on a scale of zero to 100. A stock is considered to be oversold if the RSI reading falls below 30.In the case of Silver Miners, the RSI reading has hit 28.8 — by comparison, the RSI reading for the S&P 500 is currently 57.0. A bullish investor could look at SIL's 28.8 reading as a sign that the recent heavy selling is in the process of exhausting itself, and begin to look for entry point opportunities on the buy side. Looking at a chart of one year performance (below), SIL's low point in its 52 week range is $14.94 per share, with $54.34 as the 52 week high point — that compares with a last trade of $35.19. Silver Miners shares are currently trading down about 9% on the day.