NEW YORK ( TheStreet) -- First Solar ( FSLR) insiders are selling again.

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On Monday, First Solar systems business head Jens Meyerhoff and First Solar chief technology officer David Eaglesham sold a combined $740,000 worth of First Solar shares, according to SEC filings.

It always attracts a lot of attention when insiders at the bellwether solar company are unloading insider stakes. Yet it always comes with a grain of salt, too, as these insiders are likely among the most heavily concentrated investors in their own shares. Prudent financial planning and portfolio diversification is the standby response from insiders when they sell -- and, often, it's warranted.

Nevertheless, solar investors remain interested in the share price at which First Solar insiders sell, since First Solar is the most richly rewarded solar stock from a valuation standpoint -- but also among the most targeted stocks by solar bears that see First Solar's market advantage eroding.

Meyerhoff -- who has transitioned out of the role of First Solar CFO to take over the solar company's systems business -- sold $263,000 worth of shares at a price of $131.79.

In three insider sales transactions during December, Meyerhoff sold a total of $410,000 worth of First Solar shares at prices ranging from $130 to $140.

The old low-water mark for First Solar insider selling used to be $140, but the trigger to sell seems to have been taken down a notch, with the most notable lowered threshold noted in recent First Solar selling conducted by the Walton family, founders of Wal-Mart ( WMT) and long-time First Solar shareholders.

In early December, the estate of John Walton sold First Solar shares at a share price of $122, which was the first insider sale by the Wal-Mart heirs in some time that wasn't triggered by the $140 level in First Solar shares. It was the lowest price at which the Walton estate had sold First Solar shares since August 2007, according to inside sales watchdog Insiderscore.com.

First Solar's CTO Eaglesham sold almost twice as much First Solar shares as Meyerhoff, $481,000, at a price of $132.61. Yet Eaglesham, unlike the Waltons, has shown no compunction about selling First Solar shares in the $120s.

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