There are dozens of stocks in Berkshire Hathaway's (BRK.A -0.59%) (BRK.B -0.71%) portfolio, but most of the attention goes to the major holdings, like Apple, Coca-Cola, and Wells Fargo. However, some of the portfolio's smaller holdings look rather attractive and might be worth learning about as well. Here are three of the smaller Buffett stocks in particular that you may want to take a closer look at.

When Buffett likes an insurance company, you should pay attention

Insurance has been the backbone of Berkshire's business for decades, and it continues to be so with Berkshire subsidiaries such as GEICO, General Re, and Berkshire Hathaway Reinsurance Group. In fact, in his most recent letter to shareholders, Buffett referred to insurance as "our most important sector." So, it may come as a surprise that insurance stocks are largely absent from Berkshire's stock portfolio.

Warren Buffett at Berkshire Hathaway's annual meeting.

Image source: The Motley Fool.

One notable exception is its 5.5% stake in Torchmark Corporation (GL -0.83%), which sells life and health insurance to underserved middle-income households. Life insurance makes up about 70% of the company's premium income, and supplemental health insurance plans, such as Medicare Supplement insurance, makes up the other 30%.

It's not hard to see why Buffett would like Torchmark, which has been in Berkshire's portfolio for quite some time. The company has excellent cash flow, doesn't use too much leverage, and has an aggressive share buyback program, having reduced its outstanding share count by more than 16% since 2013. Finally, Torchmark does an excellent job of generating an underwriting profit -- in fact, of five major life insurers I discussed in an article last October, Torchmark was the only one that generated an underwriting profit for the previous year.

The Buffett bank stock you haven't heard of

When most investors talk about Buffett's bank investments, they're usually referring to the company's stakes in Wells Fargo or U.S. Bancorp, or the recently added 700 million share investment in Bank of America. However, Buffett has also made some smaller banking investments, such as Berkshire's 3.5% stake in M&T Bank (MTB -1.15%).

M&T Bank has grown tremendously over the years, from $2 billion in assets in 1983 to $123 billion currently, and is among the 20 largest U.S.-based banks. Buffett first bought in to the bank in the form of preferred stock in 1991, and converted his investment into common stock a few years later.

A rarity among U.S. banks, M&T Bank has not produced a loss for 163 consecutive quarters. The bank didn't reduce its dividend during the financial crisis, and also never produced a return on tangible common equity of less than 12.3% over the past decade, which demonstrates the bank's excellent risk management.

The bank produces a 1.21% return on tangible assets, well above the 1% industry benchmark, and with an efficiency ratio of 56.9%, is among the most efficient brick-and-mortar banks.

Berkshire's first REIT

One of Berkshire's most recent purchases was a $377 million investment in a nearly 10% stake in net-lease real estate investment trust Store Capital (STOR), made through Berkshire subsidiary National Indemnity Co.

If you're not familiar with "net lease" real estate, it generally refers to freestanding single-tenant properties, where the tenants sign long-term lease obligations (with gradual rent increases already agreed upon), and are responsible for variable costs like property taxes, insurance, and some building maintenance. In other words, the REIT simply has to put a tenant in place, and enjoy years of consistently growing income. Sounds like a Buffett business to me.

Store Capital's stock price has fallen considerably over the past year or so, as have most other retail REITs, given the headwinds in that industry. However, the beauty of the situation is that most of Store Capital's tenants are service-based or otherwise resistant to e-commerce headwinds. So, this is a beaten-down stock with an extremely attractive business model.

With a 5% dividend yield and significant upside potential once the retail-sector headwinds subside, now could be an excellent long-term buying opportunity in Store Capital.