The U.S. subscription box market grew 890% between April 2014 and April 2018, according to Hitwise. That's why a growing list of companies -- including Amazon and Walmart -- are jumping on the bandwagon with their own boxes.

A recent survey of over 500 U.S. online shoppers by Clutch found that 54% now subscribe to subscription boxes, and the five top brands were Unilever's (NYSE:UL) Dollar Shave Club, Ipsy, Blue Apron (NYSE:APRN), BarkBox, and Hello Fresh.

Chart showing the five top subscription box services in America

Data source: Clutch. Chart by author.

Dollar Shave Club provides razors and grooming products for men, Ipsy offers beauty product samples, Blue Apron and Hello Fresh sell meal kits, and BarkBox offers toys, chews, and treats for dogs. All of these companies try to lock in customers by providing a steady stream of consumable products for a monthly fee.

Yet all of these services are also easy to replicate. Blue Apron is losing customers to Hello Fresh and other rivals, Ipsy competes against bigger players like LVMH's Sephora, and BarkBox faces competitors like PupBox. Over the long term, those low barriers to entry could make it tough for smaller players to survive and easier for bigger companies to conquer this booming market.