The protests in Ferguson, Missouri, over the shooting death of an unarmed black teen are nearly a month old by now, and yet shares in Taser (TASR), Image Sensing Systems (ISNS) and Digital Ally (DGLY) still are clinging to some impressive gains.

It’s almost too obvious a trade, and that’s the problem at this stage of the game.

Makers of less-than-lethal weapons, traffic identification systems and personal video recording technology for law enforcement — such as DGLY, ISNS and TASR — should all benefit from the lessons leaned in Ferguson. From the shooting to the aftermath, there were plenty of opportunities to make use of those technologies.

The risk in investing in these names after they have moved — just like any hot fad — is that the easy money has already been made. The market has already accounted for any huge influx of new business, so how much upside could be left?

On the other hand, momentum trades do have a life of their own. A stock soars, the fundamentals deteriorate … and yet the market couldn’t care less.

It’s possible to ride a hot stock to even greater gains, but be aware that the odds are against you. After all, everyone else — including professionals swinging very big lines — are trying to do the same thing.

Big Gains for DGLY, TASR and ISNS

The 0ne-month returns in this space have been downright eye-popping.

Digital Ally stock is up more than 800% on a boom in business. DGLY expects revenue to jump 26% this year thanks to a rush of police departments making inquiries about its wearable body cameras. DGLY landed a $1 million contract with Michigan’s state police department in late August; maybe that will help DGLY post its first full-year profit since 2008.

TASR stock is up “only” 53% over the past month, but it could still be the biggest winner in the not-too-distant future. Taser makes cameras as well as stun guns, but the big advantage is that it already has relationships with law enforcement agencies all over the country.

TASR was already benefiting from strong international business before the shooting in Ferguson. The U.K. has been fertile ground for Taser ever since the police there ran a successful trial program during the summer Olympics of 2012. Investors are betting that Brazil will become a large customer ahead of its hosting of the 2016 Olympics.

And ISNS stock is up nearly 300% in the last month. The company makes license-plate identification software, among other products, and business was sluggish in the first half of the year. Sales fell 20% in the second quarter. Heck, ISNS hasn’t booked a full year of net income since 2010 … and yet recently, Wall Street thought it good enough for a quadrupling.

Great for Traders, Not for Investors

This brings us to another risk with these stocks: They’re small.

TASR stock — the biggest of the bunch — has a market cap of just $894 million, making it a small small-cap.

Investors need to be concerned about volatility and liquidity — and that goes even more for super-tiny ISNS and DGLY. Even after huge runs, ISNS has a market cap of just $43 million. DGLY stands at $76 million.

TASR, ISNS and DGLY have all certainly gotten ahead of themselves by earnings and sales projections. These stocks will cool off eventually, and come down hard. In fact, they’re even starting to show signs of weakness; DGLY lost 16% by midday in Wednesday’s session.

Of course, on the other hand, ISNS jumped another 34% by midday Wednesday.

If you’re a trader, these stocks are your new best friends. But anyone looking to invest and forget need not apply.

As of this writing, Dan Burrows did not hold a position in any of the aforementioned securities.