Behold: The small, cheap device that's disrupting the $7 billion legal cannabis business.

This tiny combination of plastic, glass, and metal is a disposable cannabis oil cartridge. It costs anywhere from $30 to $70 (depending on the oil inside), is easily carried in your pocket, and produces little-to-no smell when consumed. You simply screw it into an inexpensive, rechargeable pen and inhale. That's it.

It's this tiny device that's quickly taking over cannabis consumption in America's largest cannabis market: California. Nearly a quarter of sales from 2016, tracked by marijuana delivery service Eaze, were for cartridges:

This data comes from Eaze, a marijuana delivery service that operates all over California. Eaze

Similar growth rates are showing up outside of California as well.

States like Colorado, Washington, and Oregon — where cannabis is legal — are showing massive percentage growth for "concentrates" (cannabis oil), according to BDS Analytics.

These are growth rates for 2016. BDS Analytics

Notably, this seems to be a growth trend connected to convenience.

As "flower" (traditional marijuana buds) is messy, complicated, and requires preparation to be smoked, it's no surprise that easier forms of marijuana product are growing so quickly.

Learning how to roll a joint is a hassle, as is "breaking up" (crumbling) cannabis. Sonya Yruel/Drug Policy Alliance

Though cannabis oil ("concentrates") are making huge gains, the same can be said for pre-rolled and edibles. Edibles are simply eaten, and can be "dosed" out so you don't overdo it; pre-rolled joints are as simple as lighting a cigarette — no rolling skills required. Cannabis oil marries the convenience of both.

On top of those conveniences, oil cartridges are inexpensive and travel easily. Best of all, using a cannabis oil vape produces none of the characteristic smells or clouds of smoke associated with traditional cannabis consumption.

These are sales numbers from 2016. BDS Analytics

All that growth has led to tens of millions of dollars in sales thus far, with an even brighter future expected as the market expands — despite huge wins for recreational cannabis sales in November 2016, regulation and implementation doesn't kick in until January 2018 in many states. As commercial sales begin and more of the public tries these easy-to-use, disposable cartridges, expect even more explosive growth.