There is a cluster of confusion in the rules. You can read the rules like many read the constitution (if it doesn't say you can't do something, then go ahead or by only what is there in print). In Part 95A the rules actually say that transmitters must only be certified for use in GMRS and then in the next sentence it states the rules must only meet the technical standards for GMRS...so the two sentences contradict one another. If you actually dive down into the technical standards, then they actually require a crystal controlled radio (which I might add, most of the FCC OET database only goes back to 1982 when radios began to become synthesized) but we know that since the rules were written in 1989 that Motorola, Icom, Kenwood, Standard Horizion (Vertex), and General Electric (Harris) have all manufactured synthesized radios with 90/95A certification. As a result, many just run whatever Part 90 radio they can get their hands on (because they meet technical specifications).