Want a quick way to find some quality investments? Take a look at Berkshire Hathaway's portfolio. It contains many solid companies that some of the world's smartest investors, including billionaire Warren Buffett, have vetted.

Three stocks that are not only solid investments in that portfolio but have also doubled in the past five years are Apple (AAPL 2.20%)T-Mobile US (TMUS -0.34%), and Mastercard (MA -0.22%). Let's see what the future portends for them now.

1. Apple

Apple is a favorite of Buffett's, and for good reason -- the company is a money-making machine with a loyal customer base. The company's revenue has soared and profits have risen at an even higher rate over the past five years, which has made the tech stock a hot buy for investors.

AAPL Revenue (Annual) Chart

AAPL Revenue (Annual) data by YCharts

Over the past five years, its share price has quadrupled. At a multiple of 33 times earnings, the $3 trillion company isn't a cheap buy, but it is still growing.

This year the company unveiled its Vision Pro headset, which gives users a mixed-reality experience that can be popular in the metaverse. It uses over a dozen cameras, and at a price tag of $3,499, it may quickly contribute to Apple's top line. The company is also working on a chatbot that could rival ChatGPT, paving the way for another growth opportunity in artificial intelligence.

With so much growth potential still out there for the business, it's easy to see why Apple's stock remains a popular one for growth investors. If it's successful in these new ventures, the company's valuation should continue to climb in the years ahead, making it a good long-term buy.

2. T-Mobile

T-Mobile has been another popular stock to own over the past five years, as the un-carrier has generated returns north of 140% during that time frame. The telecom company's focus on customer satisfaction at all costs has paid off. In February, J.D. Power gave T-Mobile top marks for customer care, ranking it first among mobile network operators for an 11th consecutive year.

Its merger with Sprint in 2020 expanded the company's reach and size. In 2022, revenue of just under $80 billion was 77% higher than the $45 billion it reported in 2019. And as the companies fine-tune their operations and capitalize on synergies, profitability should improve (2022 net income of $2.6 billion was actually less than the $3.5 billion profit T-Mobile posted three years ago). T-Mobile estimates that synergies from the deal could top $7.5 billion.

An increase in profitability and continued levels of high customer satisfaction should ensure that T-Mobile remains a great buy for the foreseeable future.

3. Mastercard

As of the start of July, Mastercard stock was up over 100% over the past five years. The credit card company is a great investment to hold, because as the economy grows and consumer spending rises, so too do credit card transactions. From $17 billion in revenue in 2019, the company's top line has jumped to over $22 billion this past year, for an increase of 32%. Its free cash flow has also been strong, totaling $10 billion in 2022, which is up by a similar amount (35%) from three years earlier.

One of the credit card company's future growth opportunities could come from crypto. Mastercard has partnered with multiple exchanges to offer cards linked to cryptocurrencies. The company has been focusing on making crypto more accessible to users, and even offers crypto consulting services. With the growing popularity of Bitcoin and other digital currencies, this could help drive even more growth for Mastercard in the future.

Between crypto, economic growth, and the continued strength of e-commerce, Mastercard's top and bottom lines should only get better in the long run, making it a great buy for long-term investors.