In May 1997, incompatibility between x2 and K56Flex threatened adoption of U.S. Robotics’ 56k modem because prospective buyers were wary pending a standard; the company announced a 30-day money-back guarantee. Dataquest analyst Lisa Pilgrim attributed the incompatibility to the technologies' inability to communicate ahead of an International Telecommunications Union standard, and the guarantee was unconditional for 56k modem purchases from June 1 through September 15.

U.S. Robotics said it would upgrade its 56k modems to the new international standards once established, and it would offer rebates of up to $25 to buyers who signed up with one of 350 supporting internet service providers.