Following the mass shooting at Marjory Stoneman Douglas High School in Parkland, Florida, survivors have placed intense pressure on politicians to enact stricter gun control legislation. Corporate brands with ties to the National Rifle Association (NRA) have not escaped heat, either.

Consumers across America are threatening to boycott businesses with ties to the NRA if their gun sale policies are not altered in some way.

As a result of this increased pressure, corporations like Delta and Dick's Sporting Goods are taking second looks at who they're selling guns and offering discounts to.

Here are the biggest brands who have changed their rules since the Parkland massacre—and the ones who haven't.

The Corporations Who Have Changed Their Gun Policies Post-Parkland

Dick's Sporting Goods

On Wednesday, the Fortune 500 sporting goods corporation announced that it would stop selling assault-style weapons, effective immediately. On top of that, customers must now be at least 21 years old to purchase a firearm at their stores—an example that's now been set for the company's competitors.

Walmart

Walmart said it would raise its minimum age for gun purchases from 18 to 21. They are also removing products that resemble assault rifles—like "nonlethal airsoft guns and toys"—from their website.

Kroger

America's largest supermarket chain, known for its Fred Meyer chain, raised its minimum age for gun purchases from 18 to 21.

Delta and United Airlines

Delta and United may be competing airline carriers, but they both will no longer offer discounted rates to NRA members.

As a result of this decision, a tax bill recently passed in the Georgia House and Senate that eliminates Delta's jet-fuel tax break. The tax exemption amounted to $38 million.

Hertz, Enterprise, and Avis

Three separate rental car companies—the Hertz Corporation, Enterprise Holdings, and Avis Budget Group—ended their discount programs for NRA members.

Enterprise and Avis' changes will go into effect on March 26.

MetLife

The insurance company ended discounted rates for NRA members.

L.L. Bean

The clothing and outdoor equipment retailer tweeted Thursday that it will stop selling guns and ammunition to anyone under the age of 21.

L.L. Bean tweeted a "superfan" who asked the retailer to change its policy: "In the wake of this shooting we have reviewed our policy on firearm sales, and we will no longer be selling guns or ammunition to anyone under the age of 21."

The Corporations Who Refuse to Change Their Gun Policies

FedEx

FedEx will decisively not terminate their relationship with the NRA, tweeting that "FedEx has never set or changed rates for any of our millions of customers around the world in response to their politics, beliefs or position on issues."

The company says it "opposes assault rifles being in the hands of civilians," but they will continue to offer up to a 26 percent discount to NRA members.

Roku

Streaming services like Apple, Amazon and Roku are being criticized for airing the NRA's channel, NRATV.

"We are not promoting or being paid to distribute NRA TV," Roku's responded in a statement. "We do not and have not ever had a commercial relationship with the NRA ... We welcome Moms Demand Action and other important groups to use our platform to share their messages too."

HotelPlanner

The hotel booking website's CEO, Tim Hentschel, says the company will not change their NRA discount program.

"We're a classic hospitality company," he told CNBC earlier this week. "If you ask us to be a part of your boycott war, that's not what we're about. We're about hospitality, we're about welcoming all guests."