Corporate insiders sell their own companies' stock for a number of reasons. ¿

They might need the cash for a big personal purchase such as a new house or yacht, or they might need the cash to fund a charity. Sometimes they sell as part of a planned selling program that they have put in place for diversification purposes, which allows them to sell stock in stages instead of selling all at one price.

Other times they sell because they think their stock is overvalued and the risk/reward is no longer attractive. Some even dump their own stock because they have inside knowledge that a competitor is eating their lunch and stealing market share. ¿

But insiders usually buy their own shares for one reason: They think the stock is a bargain and has tremendous upside.

The key word in that last statement is "think." Just because a corporate insider thinks his or her stock is going to trade higher, that doesn't mean it will play out that way. Insiders can have all the conviction in the world that their stock is a buy, but if the market doesn't agree with them, the stock could end up going nowhere. Also, I say "usually" because sometimes insiders are loaned money by the company to buy their own stock. Those loans are often sweetheart deals and shouldn't be viewed as organic insider buying.

At the end of the day, it's institutional money managers running big mutual funds and hedge funds that drive stock prices, not insiders. That said, many of these savvy stock operators will follow insider buying activity when they agree with the insider that the stock is undervalued and has upside potential. This is why it's so important to always be monitoring insider activity but twice as important to make sure the trend of the stock coincides with the insider buying.

Recently, a number of companies' corporate insiders have bought large amounts of stock. These insiders are finding some value in the market, which warrants a closer look at these stocks.

Nimble Storage

One data storage devices player that insiders are active in here is Nimble Storage  (NMBL) , which provides flash-optimized storage platform. Insiders are buying this stock into massive weakness, since shares have plunged by 58.9% over the last six months.

Nimble Storage has a market cap of $824 million and an enterprise value of $625 million. This stock trades at a fair valuation, with a price-to-sales of 2.78 and a price-to-book of 5.10. Its estimated growth rate for this year is 20.7%, and for next year it's pegged at 17.4%. This is a cash-rich company, since the total cash position on its balance sheet is $209.71 million and its total debt is zero.

A vice president just bought 50,000 shares, or about $516,000 worth of stock, at $10.32 per share.

From a technical perspective, Nimble Storage is currently trending well below both its 50-day and 200-day moving averages, which is bearish. This stock recently gapped-down sharply from over $20 a share to under $12 a share with heavy downside volume flows. Following that move, shares of Nimble Storage have started to stabilize and trend a bit higher off its recent low of $9.91 a share. That move is now quickly pushing this stock within range of triggering a major breakout trade above some key near-term overhead resistance levels.

If you're bullish on Nimble Storage, then I would look for long-biased trades as long as this stock is trending above that recent $9.91 low and then once it breaks out above some key near-term overhead resistance levels at $10.69 a share and then above $12 a share with high volume. Look for a sustained move or close above those levels with volume that registers near or above its three-month average action of 1.28 million shares. If that breakout fires off soon, then this stock will set up to re-fill some of its previous gap-down-day zone that started above $20 a share.

Rovi

Another stock that insider are loading up on here is Rovi  (ROVI) , which provides integrated solutions for the discovery and personalization of digital entertainment to service providers and consumer electronics industry worldwide. Insiders are buying this stock into big weakness, since shares have fallen sharply by 29.7% over the last six months.

Rovi has a market cap of $979 million and an enterprise value of $1.8 billion. This stock trades at a cheap valuation, with a forward price-to-earnings of 5.8. Its estimated growth rate for this year is -17.4%, and for next year it's pegged 41.3%. This is not a cash-rich company, since the total cash position on its balance sheet is $147.79 million and its total debt is $1.01 billion.

A director just bought 500,000 shares, or about $5.65 million worth of stock, at $10.81 to $11.54 per share.

From a technical perspective, Rovi is currently trending above its 50-day moving average and well below its 200-day moving average, which is neutral trendwise. This stock has been uptrending strong over the last month, with shares moving higher off its low of $8.01 a share to its intraday high on Tuesday of $11.93 a share. During that uptrend, shares of ROVI have been making mostly higher lows and higher highs, which is bullish technical price action. That move has now pushed this stock within range of triggering a near-term breakout trade above some key overhead resistance levels.

If you're in the bull camp on Rovi, then I would look for long-biased trades as long as this stock is trending above its 20-day moving average of $10.44 a share and then once it breaks out above some near-term overhead resistance levels at $11.93 to $12.02 a share with volume that hits near or above its three-month average action of 1.64 million shares. If that breakout develops soon, then this stock will set up to re-test or possibly take out its next major overhead resistance levels at $13 to $14, or even its gap-down-day high from July at around $15 a share.

CrossAmerica Partners 

One energy player that insiders are jumping into here is CrossAmerica Partners (CAPL) , which operates as a wholesale distributor of motor fuels, and owns and leases real estate used in the retail distribution of motor fuels in the U.S. Insiders are buying this stock into large weakness, since shares have dropped sharply by 28.2% over the last six months.

CrossAmerica Partners has a market cap of $806 million and an enterprise value of $1.25 billion. This stock trades at a reasonable valuation, with a forward price-to-earnings of 36.2. Its estimated growth rate for this year is 171.9%, and for next year it's pegged at 191.3%. This is not a cash-rich company, since the total cash position on its balance sheet is $1.86 million and its total debt is $436.67 million. This stock currently sports a dividend yield of 9.6%.

A beneficial owner just bought 59,633 shares, or about $1.45 million worth of stock, at $24.26 to $24.69 per share.

From a technical perspective, CrossAmerica Partners is currently trending below both its 50-day and 200-day moving averages, which is bearish. This stock recently formed a double bottom chart pattern, after shares found some buying interest at $22.83 to $23.25 a share. Shares of CrossAmerica Partners LP have now started to spike a bit higher above those support levels, and it's beginning to trend within range of triggering a big breakout trade above some key near-term overhead resistance levels.

If you're bullish on CrossAmerica Partners LP, then I would look for long-biased trades as long as this stock is trending above those recent double bottom support levels and then once it breaks out above some near-term overhead resistance levels at $25.11 to $26 a share and then above more key resistance levels at $27.08 to $27.87 a share with high volume. Look for a sustained move or close above those levels with volume that registers near or above its three-month average volume of 98,957 shares. If that breakout takes hold soon, then this stock will set up to re-test or possibly take out its next major overhead resistance levels at $30 to $33.68 a share, or even $35 a share.

Wesco Aircraft

One industrial equipment player that insiders are in love with here is Wesco Aircraft  (WAIR) , which distributes and provides supply chain management services to the aerospace industry in the North America and internationally. Insiders are buying this stock into notable weakness, since shares have dropped by 11% over the last six months.

Wesco Aircraft has a market cap of $1.2 billion and an enterprise value of $2.1 billion. This stock trades at a reasonable valuation, with a forward price-to-earnings of 10.6. Its estimated growth rate for this year 4.8%, and for next year it's pegged at 12.8%. This is not a cash-rich company, since the total cash position on its balance sheet is $82.87 million and its total debt is $955.77 million.

A director just bought 233,365 shares, or about $2.96 million worth of stock, at $12.36 to $12.99 per share.

From a technical perspective, Wesco Aircraft is currently trending above its 50-day moving average and below its 200-day moving average, which is neutral trendwise. This stock has been uptrending strong over the last few weeks, with shares moving higher from its low of $11.16 to its intraday high on Tuesday of $13.50 a share. During that uptrend, shares of Wesco Aircraft have been consistently making higher lows and higher highs, which is bullish technical price action. That strong uptrend has now pushed this stock within range of triggering a near-term breakout trade above some key overhead resistance levels.

If you're bullish on Wesco Aircraft, then I would look for long-biased trades as long as this stock is trending above its 50-day moving average of $12.46 a share and then once it breaks out above some near-term overhead resistance at $13.50 a share with high volume. Look for a sustained move or close above that level with volume that hits near or above its three-month average action of 324,170 shares. If that breakout gets started soon, then this stock will set up to re-test or possibly take out its next major overhead resistance levels at $14 to $14.40, or even $15 to $15.61 a share.

Exco Resources

One final stock with some decent insider buying is independent oil and natural gas player Exco Resources  (XCO) , which engages in the acquisition, exploration, exploitation, development, and production of onshore oil and natural gas properties with a focus on shale resource plays in the U.S. Insiders are buying this stock into strength, since shares have ripped higher by 32.5% over the last three months.

EXCO Resources has a market cap of $342 million and an enterprise value of $1.8 billion. This stock trades at a fair valuation, with a price-to-sales of 0.89. Its estimated growth rate for this year is -466.7%, and for next year it's pegged at 109.1%. This is not a cash-rich company, since the total cash position on its balance sheet is $20.51 million and its total debt is $1.55 billion.

A director bought 475,990 shares, or about $629,000 worth of stock, at $1.32 per share. That same director also just bought 476,000 shares, or about $559,000 worth of stock, at $1.17 per share. That same director again also just bought 738,210 shares, or about $803,000 worth of stock, at $1.08 to $1.09 per share.

From a technical perspective, EXCO Resources is currently trending above its 50-day moving average and just below its 200-day moving average, which is neutral trendwise. This stock has been uptrending strong over the last four months, with shares moving higher from its low of 48 cents per share to its recent high of $1.40 a share. During that uptrend, shares of EXCO Resources has been consistently making higher lows and higher highs, which is bullish technical price action. That strong uptrend has now pushed this stock within range of triggering a major breakout trade above some key near-term overhead resistance levels.

If you're bullish on EXCO Resources, then I would look for long-biased trades as long as this stock is trending above some key near-term support levels at $1.12 or above 95 cents per share and then once it breaks out above its 200-day moving average of $1.31 a share and then above more key resistance levels at $1.40 to $1.50 a share with high volume. Look for a sustained move or close above those levels with volume that registers near or above its three-month average volume of 2.92 million shares. If that breakout triggers soon, then this stock will set up to re-test or possibly take out its next major overhead resistance levels at $1.80 to $1.90 a share, or even $2.15 to $2.26 a share.

Disclosure: This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.