Roto Start back plate for the F & G Series Nitro Star Engines that use a 14mm hex one-way bearing. To use this back plate, your F or G Series engine must be fitted with #107829 - ONE WAY BEARING 14mm HEX FOR PULLSTART/ROTOSTART Use with any Starter unit from a Roto Start or Roto Start 2 system Please see our Roto Start Compatibility Guide to check if this is the right Roto Start system for you.