Companies with a market cap between $2 billion and $10 billion can be a fertile hunting ground for investors. These companies tend to offer proven business models and lots of room for upside if they can continue to execute on their growth plans.

So, which mid-cap stocks are smart buys today? We asked a team of Fools, and they picked Finisar (NASDAQ:FNSR)RSP Permian (NYSE: RSPP), and Veeva Systems (NYSE:VEEV). Here's why.

Business man giving thumbs up

Image source: Getty Images.

This fiber-optic discount won't be around much longer

Anders Bylund (Finisar): Shares of optical networking components maker Finisar plunged 18% lower in March and have not bounced back in the first half of April.

It's a deal. It's a steal. It's the sale of the century.

All right, maybe that's a bit over the top. But you get my point -- Finisar shares are absolutely a buy at today's compressed prices, primed for a fantastic bounce in the not-too-distant future.

The company expects large-scale orders for high-end network cards from Chinese telecoms in the second half of this calendar year. In America, the FCC just completed a major auction of wireless spectrum licenses, setting the stage for a domestic round of infrastructure upgrades. Worldwide, 5G versions of wireless connection technologies are being tested and prepped for installation, once again raising the ante for fiber-optic hookups between cell towers and the internet backbone.

These are just a few of the many growth drivers that are bubbling just under the surface right now, ready to send equipment suppliers like Finisar skyrocketing in late 2017. But share prices have fallen 20% year to date and the stock trades at just 10 times forward earnings estimates.

Finisar is a leader in an attractive market that's set to explode -- and the stock is trading at a huge discount right now.

A high-growth oil stock

Matt DiLallo (RSP Permian): After two challenging years, the oil industry has started to reset its cost structure and adjust to low oil prices. However, one area where the impact of that adjustment has been the most dramatic is in the Permian Basin of Texas, where producers can now earn exceptional returns drilling new wells at current oil prices. Because of that, drillers with acreage in the region expect to achieve remarkable growth rates in 2017 and beyond.

One company projecting truly astounding growth this year is RSP Permian. The $6 billion oil company expects its average daily production rate to rise a breathtaking 82% to 95% this year. While a recent acquisition will fuel some of that incremental production, the company's high-return drilling program will drive the rest. Meanwhile, RSP Permian expects to deliver 30%-plus annual production growth in 2018 and 2019 while living within cash flow at $55 oil.

While RSP Permian does expect to outspend cash flow slightly this year in pursuit of growth, the company can afford this since it has more than $100 million in cash and a low net-debt-to-EBITDA ratio of 2.4. In fact, the incremental cash flow from this year's wells put it on pace to push leverage below 2.0 times by the end of the year as long as oil averages $55 per barrel. Meanwhile, leverage will continue improving with future growth as long as oil stays around $55.

With its low-cost, high-return Permian position and conservative balance sheet, RSP Permian expects to achieve remarkable growth over the next few years. That makes it an excellent mid-cap growth stock to own for those that believe oil will at least hold steady for the next few years. 

A specialized software provider 

Brian Feroldi (Veeva Systems): Anyone who works for a life-sciences company knows firsthand that industry operates under its own unique set of rules. A former executive at named Peter Gassner realized this truth years ago and set out on his own to create a tailor-made software solution for this industry. He called his company Veeva Systems and he started to offer services to life-sciences businesses that no other vendor could match. That's allowed Veeva to dominate this niche and rapidly grow into the $7 billion giant that it is today.

So what does Veeva's software do? The company's cloud-based customer relationship management (CRM) platform makes it easy for pharmaceutical and biotech businesses to keep tabs on their sales force. This not only helps with target- and goal-setting, but it also ensures they remain compliant with the latest rules and regulations. What's more, the software also allows them to track which doctors are using which drugs so they can get a better view of the competitive landscape.

Companies have welcomed Veeva's solutions with open arms, which has driven huge growth in revenue and profits. Last year the company's top line jumped 33% to $540 million while non-GAAP EPS rose by 43%. These terrific results caused the stock to more than double in a single year.   

Looking ahead, Veeva is convinced that its solutions are applicable to businesses outside of the life-sciences industry. Last year the company announced that it will begin to market its solutions to companies in other regulated industries such as chemical manufacturers and consumer packaged goods companies. If Veeva finds success in these new markets, then investors will surely be rewarded.

While Veeva's stock isn't cheap, I still think the business is high-quality enough to warrant a small investment today. If you agree, then picking up a few shares today and adding more on any future weakness could prove to be a winning investment strategy.