This is a 9x7.5 airplane propeller. It is a "tractor" (not a "pusher") prop. FEATURES: Computer-optimized design gives these props a thinner profile and more "bite" with less noise. Lightweight molded nylon construction reduces rotating mass for higher output and longer life. Reinforcing carbon fibers help maintain true, constant pitch at any rpm. "C2" design (see COMMENTS). INCLUDES: One carbon-reinforced NYLON propeller REQUIRES: ALL props require balancing, this is VERY important, use TOPQ5700. May need prop reamer, use GPMQ5005 (SAE) or FOXQ1520 (Metric) SPECS: Length: 9" Pitch: 7.5 Thickness at hub: 3/8" Hole diameter: 1/4" COMMENTS: "C2" design stands for the production run in which the prop was made. dew 11/15/01