These are Rigid handle interdental brushes which facilitate changing the brush tips. These are economical options as one can buy a refill pack of the appropriate size desired. Refills are available in 5 variants.
Clean interdental gaps, as per the brush size. Unscrew the handle on top, and fit refill as per the gap size. Wash the interdental brush after use. Stop using once bristles start fraying. Some initial bleeding may occur while brushing, but will generally resolve after about 10 days.