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.

Air Products and Chemicals

One basic materials player that insiders are loading up on here is Air Products and Chemicals(APD) - Get Report , which provides atmospheric gases, process and specialty gases, electronics and performance materials, equipment and services worldwide. Insiders are buying this stock into modest weakness, since shares have dropped by 8.2% the last six months.

Air Products and Chemicals has a market cap of $28 billion and an enterprise value of $33 billion. This stock trades at a fair valuation, with a trailing price-to-earnings of 22.2 and a forward price-to-earnings of 16.1. Its estimated growth rate for this year is 12.5%, and for next year it's pegged at 9.9%. This is not a cash-rich company, since the total cash position on its balance sheet is $224 million and its total debt is $5.88 billion. This stock currently sports a dividend yield of 2.5%.

The CEO just bought 50,000 shares, or about $6.31 million worth of stock, at $126 to $127.53 per share.

From a technical perspective, Air Products and Chemicals 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 off its low of $114.64 to its intraday high on Tuesday of $132.34 a share. During that uptrend, shares of Air Products and Chemicals have been consistently making 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.

If you're bullish on Air Products and Chemicals, then I would look for long-biased trades as long as this stock is trending above its 50-day moving average of $128.44 a share or above more near-term support at $125 a share and then once it breaks out above some near-term overhead resistance levels at $132.50 to $133.91 a share with high volume. Look for a sustained move or close above those levels with volume that hits near or above its three-month average action of 1.59 million 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 its 200-day moving average of $136.19 to $140, or even $143 to $147 a share.

Zions Bancorporation

Another financial player that insiders are jumping into here is Zions Bancorporation(ZION) - Get Report , which  provides a range of banking and related services in Arizona, California, Colorado, Idaho, Nevada, New Mexico, Oregon, Texas, Utah, Washington and Wyoming. Insiders are buying this stock into big weakness, since shares have dropped sharply by 30.9% over the last six months.

Zions Bancorporation has a market cap of $4.4billion and an enterprise value of -$1.5 billion. This stock trades at a cheap valuation, with a trailing price-to-earnings of 17.9 and a forward price-to-earnings of 9.6. Its estimated growth rate for this year is 55%, and for next year it's pegged at 19.9%. This is a cash-rich company, since the total cash position on its balance sheet is $7.57 billion and its total debt is $1.16 billion. This stock currently sports a dividend yield of 1%.

The CEO just bought 50,000 shares, or about $1.13 million worth of stock, at $22.58 to $22.70 per share. The CFO also just bought 25,000 shares, or about $554,000 worth of stock, at $22.14 to $22.17 per share.

From a technical perspective, Zions Bancorporation is currently trending well below both its 50-day and 200-day moving averages, which is bearish. This stock has been downtrending badly over the last three months, with shares falling sharply lower off its high of $31.12 to its new 52-week low of $20.33 a share. During that downtrend, shares of Zions Bancorporation have been consistently making lower highs and lower lows, which is bearish technical price action. That said, this stock has started to rebound a bit off that $20.33 low, and it's now beginning to trend within range of triggering a near-term breakout trade.

If you're in the bull camp on Zions Bancorporation, then I would look for long-biased trades as long as this stock is trending above its new 52-week low of $20.33 a share and then once it breaks out above its 20-day moving average of $22.81 to some more near-term overhead resistance at $22.92 a share with volume that hits near or above its three-month average action of 3.44 million shares. If that breakout materializes soon, then this stock will set up to re-test or possibly take out its next major overhead resistance levels at $24 to $25, or even its 50-day moving average of $26.20 a share.

Polaris Industries

One recreational vehicles player that insiders are active in here is Polaris Industries(PII) - Get Report , which designs, engineers, manufactures and markets off-road vehicles, snowmobiles, motorcycles and small vehicles primarily in the U.S., Canada, Western Europe, Australia and Mexico. Insiders are buying this stock into massive weakness, since shares have plunged by 44.8% over the last six months.

Polaris Industries has a market cap of $4.9 billion and an enterprise value of $5.2 billion. This stock trades at a reasonable valuation, with a trailing price-to-earnings of 11.2 and a forward price-to-earnings of 10.5. Its estimated growth rate for this year is -4.9%, and for next year it's pegged at 11.2%. This is not a cash-rich company, since the total cash position on its balance sheet is $155.35 million and its total debt is $463.28 million. This stock currently sports a dividend yield of 2.9%.

A director just bought 6,925 shares, or about $498,000 worth of stock, at $72 per share.

From a technical perspective, Polaris Industries is currently trending below both its 50-day and 200-day moving averages, which is bearish. This stock has been uptrending a bit over the last few weeks, with shares moving higher off its low of $67.80 to its intraday high on Tuesday of $76.30 a share. During that uptrend, shares of Polaris Industries 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.

If you're bullish on Polaris Industries, then I would look for long-biased trades as long as this stock is trending above some near-term support levels at $73 to $70 a share and then once it breaks out above some near-term overhead resistance levels at $78 to its 20-day moving average of $78.71 a share with high volume. Look for a sustained move or close above those levels with volume that hits near or above its three-month average action of 1.49 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 $82 to $84, or even its 50-day moving average of $88.67 a share.

Total Systems Services

One credit services player that insiders are in love with here is Total Systems Services(TSS) - Get Report , which provides electronic payment processing services to banks and other financial institutions in the U.S., Europe, Canada, Mexico, and internationally. Insiders are buying this stock into notable weakness, since shares have fallen by 26.1% over the last three months.

Total System Services has a market cap of $7.1 billion and an enterprise value of $8.3 billion. This stock trades at a fair valuation, with a trailing price-to-earnings of 19.8 and a forward price-to-earnings of 13.6. Its estimated growth rate for this year is 6.1%, and for next year it's pegged at 9.2%. This is not a cash-rich company, since the total cash position on its balance sheet is $389.33 million and its total debt is $1.44 billion. This stock currently sports a dividend yield of 1%.

A director just bought 12,500 shares, or about $500,000 worth of stock, at $40.01 per share.

From a technical perspective, Total Systems Services is currently trending well below both its 50-day and 200-day moving averages, which is bearish. This stock recently gapped-down sharply from around $46 a share to under $40 a share with heavy downside volume flows. Following that move, this stock went on to print a new low at $37.57 a share, before rebounded back towards $40 a share. That rebound has now pushed this stock within range of triggering a near-term breakout trade.

If you're bullish on Total Systems Services, then I would look for long-biased trades as long as this stock is trending above its recent low of $37.57 a share and then once it breaks out above some near-term overhead resistance levels at $40.28 to its gap-down-day high of around $42 a share with high volume. Look for a sustained move or close above those levels with volume that hits near or above its three-month average action of 1.97 million shares. If that breakout triggers soon, then this stock will set up to re-fill some of its previous gap-down-day zone that started near $46 a share.

Kinder Morgan

One final stock with some big insider buying is energy player Kinder Morgan(KMI) - Get Report , which operates as an energy infrastructure and energy company in North America. Insiders are buying this stock into massive weakness, since shares have plunged by 57.7% over the last six months.

Kinder Morgan has a market cap of $32.6 billion and an enterprise value of $76.8 billion. This stock trades at a premium valuation, with a trailing price-to-earnings of 104.6 and a forward price-to-earnings of 17.8. Its estimated growth rate for this year is 1.4%, and for next year it's pegged at 12.3%. This is not a cash-rich company, since the total cash position on its balance sheet is $229 million and its total debt is $43.23 billion. This stock currently sports a dividend yield of 3%.

A director just bought 180,000 shares, or about $2.55 million worth of stock at $14.20 per share. From a technical perspective, Kinder Morgan is currently trending below both its 50-day and 200-day moving averages, which is bearish. This stock has been trending sideways and consolidating over the last few weeks, with shares moving between $13.95 on the downside and $16.47 on the upside. Any high-volume move above the upper-end of its recent sideways trending chart could trigger a big breakout trade for shares of Kinder Morgan.

If you're bullish on Kinder Morgan, then I would look for long-biased trades as long as this stock is trending above some near-term support at $13.95 or above more support around $12.50 a share and then once it breaks out above some near-term overhead resistance levels at $16 to $16.47 a share and then above more resistance at $17.30 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 43.89 million shares. If that breakout gets set off soon, then this stock will set up to re-test or possibly take out its next major overhead resistance levels at $20 to $22, or even $24 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.