Hi there
Japan based BEAT1RACING have introduced to limited edition parts which MUTO Front pulley adapter for RG BK3R You can more select gear ratio if you put Muto front pulley adapter.Especially Japan track layout is not like euro track layout also size. so more compact size. Muto thought need to select more gear ratio for suitable home track. 48pitch spur gear is available everywhere. If you are interested in new front pulley adapter . please feel free contact me anytime.
Source : BEAT1RACING