Talon front sprocket for use with the 520 chain.
(Now come branded as Apico!, but still made by Talon for them. ) 
Fits-
Montesa 4RT 2005 - 2013
Montesa Repsol 2005 - 2013
Honda 4RT 2014 - Onwards
Repsol 2014 - Onwards
RR 300 2016 - Onwards
4 Ride 2016 - Onwards
301rr 2020- Onwards