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In the last few years, a lot of online mattress startups have popped up. They’ve taken out the middlemen and the accompanying costs of showrooms. As a result, the same or superior mattresses are offered for less money and hassle than the brick-and-mortar store.

Of the many startups out there, Casper may be king.

The company has become synonymous with successful online startups, and has expanded from its first mattress sale in 2014 to begin selling sheets (which we reviewed here), pillows (find our review here), and even dog beds. (you bet we had one of our dogs try the bed). It also doesn’t hurt that every mattress comes with a 100-night money-back guarantee and a 10-year warranty, which is pretty much par for the course in the industry.

In other words, Casper is a grown-up cult-favorite, and the company owes a lot of that success to a really great mattress, the convenience of no-hassle home delivery, and pretty awesome prices.

On a regular day, you can get the company's best-seller, The Casper, from $595 for a twin size, and the streamlined Essential mattress from as low as $350. The upgraded high-end mattress, The Wave, comes in at $1,250 to start.

For Cyber Monday, Business Insider readers can get an exclusive 15% mattresses when they apply the code "BICM15" at checkout. So, for example, if you add a queen-size Casper Wave Mattress ($2,250) to your cart, you'll save $337.50 on your purchase.

If you've been meaning to get a new mattress - or bedding of any kind - now is a great time to act. Casper's prices are already low to remain competitive, and sales don't happen often.

Get 15% off Casper mattresses with the code "BICM15"

If you're interested in learning more before committing to a Casper mattress, these guides will help you out:

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Foto: sourceShayanne Gal / Business Insider

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