Brandon Mullins wasn’t expecting an Amazon order this week, but when he opened the parcel delivered to his home in New York City, he found a protein bar sample and a note from the e-commerce giant.

It wasn’t a fluke. Mullins has a protein powder subscription on Amazon, so he was exactly the type of customer that nutrition company BSN wanted to target with a sample of its Protein Crisp bars. His box was one of 100,000 sent out in the past week, according to Kris Gerulski, marketing director at BSN North America.

"It's beautiful because it is all based on purchase behavior. Every single sample we sent of this protein crisp bar, those 100,000 homes have never bought that product before,” Gerulski said.

“We use our positioning in the Amazon behavioral data world, then we rip it loose and they do all of the shipments."

Gerulski declined to say how much BSN pays Amazon to send its samples, but he said the price is “no different than what you pay for experiential marketing elsewhere.”

Sampling programs have been available in various iterations on Amazon over the years, including one program that allowed Prime members to purchase trial size products.

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But Mullins’ box, which drew some attention when he posted it to Twitter, adds to growing anticipation that Amazon is working on new ways to capitalize on its user data to boost purchases.

Amazon’s newest ad format, the physical ‘sample’ box, just hit my mailbox based on purchase history. Interesting if/how this scales where brands pay for the samples vs consumer $ for samples eg Birchbox cc:@natives @BenMullin @CaseyNewton @TaylorLorenz @mims pic.twitter.com/9qAU4gl7H0 — Brandon Mullins (@brandonmullins) February 26, 2019

Amazon’s current sampling program has been under the radar and lists 20 products on its website, including BSN’s Protein Crisp, Maybelline mascara and Oxi-Clean. Many customers don’t know about the program until they actually receive a sample, which also includes a note with instructions on how to opt out if they don’t want to receive another sample.

While Amazon could conceivably send every single user a highly targeted sample, the company also runs the risk of alienating users at a time when data privacy is becoming a greater concern.

“If targeted advertising creeps us out in the online world, it is reasonable that this will be amplified when you are targeted at home,” said Nancy Gray, a professor of marketing at Arizona State University’s W.P. Carey School of Business.

Last year, BSN participated in the sample program and sent 80,000 samples of another nutrition product to customers over the span of 4 to 6 months, according to Gerulski. The samples included a web address to BSN's products on Amazon, allowing the company to track how many people made purchases after receiving samples.

The company liked the conversion rate, so they decided to ramp up their participation this year, Gerulski said.

Brian Watkins, vice president of e-commerce at Bulletproof, said the company sent between 50,000 and 100,000 samples last year through the program. The company’s Brain Octane Oil is currently one of the items listed on the Amazon Samples page.

“We see Amazon’s sampling program as an extension of our broader field marketing campaign featured in Whole Foods, Wegmans and elsewhere,” Watkins said. “By working with Amazon, we mutually develop a specific set of targets and metrics we wish to achieve similar to other trial programs we have in place.”

Gray said the tactic of sending samples in the mail has been going on for more than a century. In the late 1800s, The Pears Soap Company data mined birth announcements in the newspaper and sent new parents a bar of soap and information on how to care for their baby.

“People feel obliged to reciprocate when someone does something nice for them. In other words, a gift invokes the principle of reciprocation,” she said. “This principle transcends time and social boundaries. It is reasonable that Amazon’s gift boxes will delight many and lead to brand loyalty and increase in purchasing on Amazon.”

Mullins, who leads off-platform content for Twitter, said he would try the protein bar and consider the brand in the future, since he’s “agnostic” about the protein he buys. However, he did have one suggestion for Amazon.

“One obvious consumer experience improvement need: allow me to easily transition from physical sample to ‘add to cart,’” he said. “When I open the Amazon app next, I should see an alert for ‘buy the product we sampled for you,’ or since Amazon knows I own an Alexa, it should include instructions on the insert card to ‘tell Alexa to order the protein bar sample.’”