Exchange-traded funds offer a convenient way to invest in sectors or niches that interest you. If you expect industrial companies to start doing well again once the global economy starts heating up, the Vanguard Industrials ETF (NYSE: VIS) could save you a lot of trouble. Instead of trying to figure out which companies will perform best, you can use this ETF to invest in lots of them simultaneously.

The basics
ETFs often sport lower expense ratios than their mutual fund cousins. The Vanguard ETF's expense ratio -- its annual fee -- is a very low 0.19%. (Vanguard is known for low fees.)

This ETF has performed rather well, beating the world market over the past three and five years -- which represent a tough environment. As with most investments, of course, we can't expect outstanding performances in every quarter or year. Investors with conviction need to wait for their holdings to deliver.

With a low turnover rate of 5%, this fund isn't frantically and frequently rejiggering its holdings, as many funds do.

What's in it?
Some industrial companies had strong performances over the past year. General Electric (NYSE: GE) was one, up 9%. It recently signaled that its turnaround was well under way when its GE Capital division said it would resume paying its parent company a dividend. GE has been investing in traditional and alternative energies and the mining industry, and it offers investors great diversification, as well as a dividend yield that recently topped 3%.

Other companies didn't do as well last year, but they could see their fortunes change in the coming years. Railroad company CSX (NYSE: CSX) shed 12%, but is poised to benefit as our economy picks up and companies up the volume of gods and supplies that are shipped back and forth across the nation. (Railroads are about three times as energy efficient as trucks.) CSX has also been hiring hundreds of veterans, and pleasing its investors with continued revenue growth as well as rising profit margins.

Engine maker Cummins (NYSE: CMI) fell 15% but stands to profit from a growing interest in natural-gas-powered vehicles, as it makes engines that run on natural gas. Europe's crisis has put some pressure on the company, but truck sales in North America are picking up, and Cummins also does business in more rapidly growing emerging markets.

Waste Management (NYSE: WM), meanwhile, dropped 7%, but few businesses are as assured as garbage and recycling, where it dominates. The stock was downgraded by Wall Street recently because of concerns about rising costs and falling prices for recycled commodities. Some Fools worry about the company focusing more on growth-by-acquisition rather than organic growth. For those with faith in the company, though, it offers a dividend yield north of 4%. It has embraced innovation, too, producing energy from some of its garbage.

The big picture
Long-term demand for industrial goods and services isn't going away anytime soon. A well-chosen ETF can grant you instant diversification across any industry or group of companies -- and make investing in and profiting from it that much easier.

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This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.