With industry consolidation still ongoing in the tobacco industry, and the close ties all the global cigarette giants have with one another, buying the stocks of just one or two gives you exposure to a full portfolio of combustible cigarette alternatives.British American Tobacco (NYSEMKT:BTI), for example, is in the process of buying Reynolds-American (NYSE:RAI) (a company in which it already had a 42% stake) in no small part because of the latter's market-leading e-cigarette devices.Philip Morris International (NYSE:PM), which was once part of Altria (NYSE:MO), still has close ties with its former parent (and rumors abound that one may yet buy the other), and they continue to forge deals to globally market e-cig products together under the Marlboro brand.However, although it was an early entrant in the e-cigarette segment with its MarkTen brand, and thanks to its purchase of Green Smokes, Altria has always seemed something of an afterthought in the space.So, given that buying any one stock is pretty much getting a two-fer, so let's see what the three e-cig leaders bring to the table.

When British American Tobacco completes its acquisition of Reynolds, it will vault ahead of Philip Morris to become the biggest tobacco company.It has several cigarette alternatives on the market now, but like many in the industry, it is betting that heat-not-burn (HNB) technology will be the next big advance in the niche.Unlike traditional cigarettes, which of course burn tobacco to drive the flavor and nicotine to the smoker, or earlier versions of electronic cigarettes that heat a nicotine-infused liquid, HNB devices heat real tobacco to the point of creating a vapor that delivers the taste and nicotine to the user.Because that vapor doesn't contain the toxic chemicals released when tobacco is burned, they're a healthier alternative.And they provide manufacturers with a steady stream of recurring revenue since the tobacco-filled "cigarette" must be replaced after use.BAT rolled out its HNB product -- the iFuse glo -- first in Japan.The company noted in its preliminary earnings report that in the 10 weeks the iFuse glo has been on the market there, its consumables had quickly gained a 5.4% share.

A worldwide launch is planned.BAT is currently in 12 markets with its various e-cig devices -- it markets traditional and hybrid e-cigs under the iFuse brand too -- and it plans to double the number of markets where they're present this year with a goal of doubling them again in 2018.It is marketing the glo's disposable Neostik cigarettes under the Kent brand, and has invested more than $1 billion in building a completely new next-generation product division.Reynolds was an early player in the electronic cigarette game.It purchased blu eCig for $135 million in 2012 and built it into the biggest brand on the market with about 50% of the total share, then sold it to Imperial Tobacco as part of a package deal to avoid anticompetitive issues when it purchased Lorillard.By then, however, Reynolds was already investing heavily in its Vuse e-cig product, which has since become the market leader in the U.S.with a 38% share -- more than twice that of blu, which has fallen to 16%.Altria's MarkTen has slipped to third place with a 13% share.

It is currently working on a new HNB device called Core, but Reynolds was actually first in this space too, having introduced the Eclipse back in the early 1990s, though it was ahead of its time and didn't go anywhere.e cigarette nhoss lounge avisIt attempted to relaunch the product again in 2014, this time rebranding it as Revo, but that, too, came to naught.e cigarette mockupWhether it will have any more success with Core remains to be seen, but word is that this new technology that has piqued British American Tobacco's interest, and is one impetus for their merger.e cigarette noyelle godaultGlobal tobacco industry heavyweight Philip Morris International is also a leader in electronic cigarettes with its iQOS device, a rechargeable, pen-like device into which a short, cigarette-like product is inserted.e cigarette pipe mod malaysia

Like BAT's Kent Neosticks, Philip Morris is marketing its consumable HeatSticks under the Marlboro brand.The device really changed how people viewed e-cigs -- which had begun to see their popularity wane -- because it relied upon real tobacco for flavor rather than a flavored e-liquid.e cigarette quoi choisirSince it was closer to the smoking experience users were looking for, it quickly gained in popularity, and PM is urgently planning for "a smoke-free future."e cigarette pipe mod malaysiaPhilip Morris may quickly come to dominate the U.S.electronic cigarette market, and effectively stub out all competition, if it wins FDA approval for a "reduced-risk" designation.Though it seems obvious that e-cigs and vapor products generally would be less unhealthful than traditional cigarettes, manufacturers can't market them as a safer alternative without first showing proof to regulators that they really are less dangerous.

That's a lengthy and expensive process, one that only the biggest tobacco companies can afford.It's reported that PM's application was 2 million pages long, yet it may give Philip Morris the chance to be the first to earn the ability to tell consumers its e-cigs are safer, a development that could give it a huge competitive advantage and change how electronic cigarettes are seen.Will e-cigarettes ever replace traditional cigarettes?Big tobacco companies think so, but consumers and regulators aren't so sure.E-cigs vaporize liquid nicotine cartridges into vapor, so no cancer-causing tar or smoke is inhaled.Proponents claim that e-cigs aren't more dangerous than nicotine gum or patches, and that their similarity to cigarettes makes them ideal smoking cessation devices.Opponents point out that nicotine might cause heart problems, while certain chemical additives can be dangerous.Over the past few years, tobacco companies have invested in e-cigs to offset declining shipments of traditional cigarettes.

But despite the hype, the overall market is small.According to Nielsen data, the size of the entire e-cigs market was just $1.4 billion in 2014.By comparison, the top three U.S.tobacco companies -- Altria Group (NYSE:MO), Reynolds American (NYSE:RAI), and Lorillard (NYSE:LO) -- generated combined sales of $40 billion last year.Although the e-cig market remains small, investors should still recognize which companies control the main brands in the market.Altria GroupAltria, the maker of Marlboro cigarettes, launched its MarkTen e-cigarette nationwide last year.Altria hasn't disclosed exactly how many e-cigs it has shipped, but recent Nielsen data indicates that it only controls about 6.1% of the overall U.S.Nonetheless, the MarkTen brand has continued to evolve with new e-cig flavors and the MarkTen XL, which has twice the battery life of the original.Altria also acquired premium e-cig brand Green Smoke, which is sold in the U.S.and Israel, last year to complement MarkTen's growth.E-cigs belong to Altria's smokeless products group, which also includes snuff.

Last quarter, Altria's smokeless revenue rose 3.6% annually to $430 million, which accounted for just 7.4% of its top line.Reynolds AmericanReynolds American launched its Vuse e-cig nationwide last year.Vuse is currently the top brand in the U.S.e-cig market, with a 35.7% market share.Vuse was one of the first e-cigarettes to use a computer chip to regulate puffs to deliver consistent flavor and track usage.The FTC recently cleared Reynolds to acquire Lorillard, the third largest domestic tobacco company after Altria and Reynolds, for $25 billion.But as part of the deal, Lorillard had to sell several of its brands, including Blu e-cigarettes, to U.K.-based Imperial Tobacco Group (NASDAQOTH:IMBBY).If Reynolds had kept Blu, which has a 22.7% share of the U.S.market, it would have dominated over 58% of the market.Reynolds American classifies Vuse in its "All Other" category, where Reynolds' Zonnic nicotine gum can also be found.Last quarter, revenue at the segment rose 45.3% annually to $77 million, but only accounted for 3.7% of Reynolds' top line.

Imperial TobaccoImperial Tobacco, the fourth largest international tobacco company by market share, has become another top stock to watch in e-cigs due to its acquisition of Blu.Imperial also owns Puritane, an e-cig which is marketed as a health care product in the U.K.through a partnership with the Boots pharmacy chain.Earlier this year, it launched Jai, another e-cig for the French and Italian markets.Imperial doesn't report revenue from smokeless products like snuff separately from smokeable ones like cigarettes.Instead, it categorizes them all as tobacco products.Its subsidiary, Fontem Ventures, handles the e-cig business, but it's unclear how much revenue the unit actually generates.Nonetheless, Imperial Tobacco is a top brand to watch in the e-cig market because it owns two new brands in Europe and an established one in the U.S.However, American investors without access to the London Stock Exchange can only buy ADR shares of Imperial Tobacco on the OTC market, so due diligence is advised.