There are a lot of iPhone cases to choose from — from super-protective ones to colorful, fun options.

But here's one suggestion: Don't buy one that looks like a gun.

U.S. police departments are posting pictures to social media sites of gun-shaped phone cases, along with warnings not to buy or use them for reasons that should be obvious. In a back pocket, the case looks like the grip of a pistol.

The Ocean County Prosecutor's Office in Tom's River, New Jersey, posted a picture this week of a gun-shaped iPhone case on Facebook, noting it's "not a cool product or a good idea."

Please folks - this cell phone case is not a cool product or a good idea. A police officers job is hard enough, without... Posted by Ocean County Prosecutor's Office on Monday, June 29, 2015

"A police officer's job is hard enough, without having to make a split second decision in the dark of night when someone decides without thinking to pull this out while stopped for a motor vehicle violation," the post reads.

The New York City Police Department's 112 Precinct weighed in with a similar message on Twitter:

I would NOT suggest purchasing this cell phone case, which was designed to look like a firearm. #BeSmart #BeSafe pic.twitter.com/swsWzD1sdY — NYPD 112th Precinct (@NYPD112Pct) June 30, 2015

While authorities are advising people not to buy gun-shaped iPhone cases, they're still available for purchase on places like Amazon (for $4.99 a pop) and in Japan on Japan Trend Shop (for a hefty $49).

Reviewers on Amazon are urging the company to stop selling the cases, citing the dangers.

"I highly recommend that you remove this product from your website right now!" one review reads. "Your corporate attorneys will thank you, as will the law enforcement officers who might otherwise be put into a tragic and unnecessary lethal force situation."

The timing — why police are posting these images now — is unclear. A CNNMoney report indicates that the image was circling around private forums for cops.

Amazon does not have a comment for this story.

Updated 07/02/2015 4:10 p.m. EST:

Mashable spoke to Al Della Fave, spokesperson for the Ocean County Prosecutor's Office, who originally posted the highly-circulated picture on Facebook. Della Fave is a retired firearms instructor who found the image via a friend's posting in a private Facebook for retired cops.

Della Fave told us that he's seen no issues relating to this case, but posted it to Facebook as a way to raise awareness of its existence. He said that people who are drawing weapons usually do so from their back pockets, so this case could be very easily thought to be a gun.