The market for single cup roasters is estimated at $4 billion, according to Reuters. Single cup coffee roasters are growing in popularity, especially in business offices and waiting rooms. Naturally, coffee roasters like Green Mountain Coffee (GMCR) and Starbucks (SBUX) want a piece of the action.

The single cup roasters provide several advantages to having coffee in larger coffee pots. For one thing, coffee which sits for hours in a pot loses some of its fresh flavor or becomes bitter. Enter the single cup roaster. You simply pop a small container of coffee in the machine, and viola, you get a single cup of coffee with little or no mess, and always fresh.

"One of the guiding principles of our growth investing system is the concept that major trends tend to persist longer and go farther than originally expected," says Timothy Lutts.

In The Cabot Stock of the Month, he explains, "It's a principle that supports our current bullish market stance and our recommendation of Green Mountain Coffee Roasters (NASDAQ: GMCR), even though the stock is already up more than four-fold since March."

"The business, of course, is coffee, a true global mass-market product. And while Starbucks' stock peaked in 2006 (ending a 14-year run), Green Mountain Coffee Roasters is younger and far less famous.