Secretary) to the ACO. (ii) With respect to any future payment models involving two-sided risk, Medicare fee-for-service beneficiaries who are assigned to the ACO, as determined by the Secretary. (C) Qualifying service For purposes of this subsection, a qualifying service is a primary care service, as defined in section 425.20 of title 42, Code of Federal Regulations (or in any successor regulation), with respect to which coinsurance applies under part B, furnished through an ACO by— (i) an ACO professional described in subsection (h)(1)(A) who has a primary care specialty designation included in the definition of primary care physician under section 425.20 of title 42, Code of Federal Regulations (or any successor regulation)