Right, and you SHOULDN'T use a 20A plug with this 15A receptacle, even though the circuit itself is rated at 20A. You CAN have a hypothetical 5A plug on a hypo

Right, and you SHOULDN'T use a 20A plug with this 15A receptacle, even though the circuit itself is rated at 20A. You CAN have a hypothetical 5A plug on a hypothetical 50A circuit. The plug is instructive to the user NOT to pass more than 5A through it, and since the circuit is rated at max 50A, it will not cause a fire at 5A from the abiding user. In this RV case, you are putting a hypothetical {30,50}A plug on a {15,20}A circuit (VERY BAD!) using this unsafe adapter. Your RV can EASILY exceed the maximum rated amps through this plug (since that is how it is DESIGNED -- with a special plug to set this high-current expectation which shouldn't be intentionally defeated to protect against this user "stupidity") and it CAN and WILL start a fire if someone uses this dangerous adapter, the AC kicks on, and the breaker fails or is not installed properly. This situation is analogous to cheater plugs. I used a cheater plug with a Macbook Pro in a house with only two-prong outlets, and the aluminium shell felt tingly, but the house electrical system and the circuit design of the laptop motherboard, the chassis design, and SMPS in the charger still DO have other ways of protecting my life from electocution by preventing the chassis from unexpectedly shorting with AC line voltage, even without a proper ground. If these fail, I am dead. Regardless, I was admittedly an idiot for circumventing one safety system to intentionally fallback on others, which weren't necessarily designed to protect against my own idiocy since the assumption was that there is a proper ground. * FWIW, I have friends in my hometown that are electricians, I helped my dad (properly) wire our basement, and I have an electrical engineering degree myself.