It's a cost-control strategy called "reference pricing."
It puts a hard dollar limit on what health plans pay for certain expensive procedures - like knee and hip replacements.
The Obama administration has given the go-ahead for insurers and employers to use the approach, setting aside some legal concerns.
Some experts worry that patients could be surprised with big medical bills they must pay themselves, undercutting financial protections in the new health care law. That would happen if patients picked a more expensive hospital.
Other experts say the new strategy helps keep premiums in check.
The administration's decision affects most job-based plans as well as the new insurance exchanges.