This is the OS Type F 4-Stroke Glow Plug.  The OS Max #F Glow Plug is designed epecially for OS Max and other brand Four-Stroke R/C Engines.

Features:

• Specially shielded long-reach plug for use in O.S. (and other) four stroke engines. Shield keeps plug hot for lower idle RPM
• For use with fuels with a 5-15% nitro content

Includes:
One #F Glow Plug (without idle bar)
One brass glow plug gasket