You do not buy an SR-22 or an FR-44 on its own. You buy auto insurance from a company willing to file one, and that company sends the filing to the state on your behalf.
The FLHSMV insurance requirements page calls the SR-22 "an insurance filing" and names the two coverages it vouches for, bodily injury liability and property damage liability, as a way to meet reinstatement requirements under Florida's Financial Responsibility Law. The FR-44 does the same kind of job for the higher limits that s. 324.023 sets after a DUI.
