Roto Start back plate for the F and 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 the one-way bearing 14mm hex for pull start/Roto Start. Use with any starter unit from a Roto Start or Roto Start 2 system. Please check the Roto Start compatibility guide to ensure this is the right Roto Start system for you.