Gone are the days of flopping onto mattress after mattress in a stuffy showroom floor.

Online mattress companies that ship to your front door say that finding the perfect bed might just take a few clicks. But experts warn that it’s important to look beneath the sheets. They say many mattresses being sold are actually very similar — despite how they’re marketed.

“The products that you’re buying — there are many similarities and only some minor differences,” said Seth Basham, an analyst at Wedbush Securities who covers the mattress industry. He said that the core of the mattresses at different companies often use the same foam. “The different layers — what goes on top of what, can differ. But the big difference is how they’re being sold and marketed.”

There are now around 175 bed-in-a-box companies in business, estimated Michael Magnuson, founder of mattress review site GoodBed.com. Their sales account for 12% of the $16.5 billion mattress industry, though only the top 10 companies make a significant dent, according to Basham. Among the major players are brands like Purple, Casper, Nectar, Leesa, and Tuft & Needle.

Mattress giants like Tempur Sealy and Serta Simmons should be nervous, said Peter Keith, an analyst at Piper Jaffray. Sales units on average at those companies have been down 5% over the past two years.

A survey by the International Sleep Products Association reported that 45% of mattresses purchased in last year were online, up from 35% for purchases in 2017.

Purple is the only public bed-in-a-box company, after it merged with a public investment shell company in 2018 at a valuation of $1.1 billion. Its stock has dropped 40% since the merger, and the company is currently valued at $355 million. Like many other bed-in-a-box companies, according to Basham, Purple has not yet seen a profit. In 2018, the company made $285 million in sales, and reported a net loss of $19.6 million.

Profit is hard to come by because the ease of forming an online mattress company makes the market competitive, according to Basham. “Barriers to entry are low, but barriers to profitability are high,” he said. “It doesn’t take that much to design a mattress, a marketing campaign, put up a website, and have one of these big companies like Carpenter do the fulfillment for you,” he said, referring to one of the key mattress manufacturing companies.