The specific legal silencers for Royal Enfield motorcycles in 2020 can vary depending on the country or region you are in, as different countries have different regulations and requirements regarding vehicle modifications and exhaust noise levels.
In general, it's important to comply with local traffic laws and regulations when considering a silencer for your Royal Enfield motorcycle. Many countries have noise regulations in place to ensure that vehicles meet certain noise emission standards to minimize noise pollution.
To determine which silencers are legal for your Royal Enfield motorcycle in your specific area, I would recommend consulting local transportation authorities or referring to your country's vehicle regulations and emissions standards. These authorities will have the most up-to-date and accurate information regarding the permissible silencer options for your motorcycle model and the corresponding legal requirements.