Genuine Honda left grip for the CRF and XR models listed. Cut off your old grips, put some grip glue on the handlebar, and use a very small amount of soapy water on the inside of the grip to slide it on. Try not to stop half way because the grip glue cures quickly.
Honda Part Number: 53166-GEL-305
Fits Honda:
CRF50F - 2004-2009, 2011-2012
XR50R - 2000-2003