The Yamaha RT100 is a small off-road motorcycle that was produced in the 1990s. While I can provide some general guidance, it's important to note that specific part compatibility can vary depending on the year and model of your RT100. To ensure the correct air filter fitment, it's best to consult the owner's manual, contact a Yamaha dealer, or refer to reputable motorcycle parts suppliers.
That being said, the most common air filter for the Yamaha RT100 is the Uni Filter NU-2213ST. Uni Filter is a well-known brand that manufactures high-quality air filters for motorcycles and off-road vehicles. The NU-2213ST air filter is designed to fit Yamaha RT100 models and offers excellent filtration and protection against dust and debris.
Consulting with a Yamaha dealer or using online parts lookup tools can help you find the accurate air filter for your motorcycle.