OEM Honda thermostat and OEM o-ring for the Honda CBR250RR MC22. It also fits the Honda RVF400 NC35 and the Honda CBR400RR NC29
The Honda part number is 19300-ML7-003 (19300ML7003) and 91311-KE8-000 (91311KE8000)
These are genuine Honda thermostats designed for the RVF400 NC35, and interchangeable with the Honda CBR250RR MC22 and the Honda CBR400RR NC29
If you find your bike takes a while to get warm, your thermostat may need replacing. As they are constantly submerged in fluid and subject to countless heat cycles, the performance of thermostats tend to degrade over time.