This is a 16 Tooth Clutch Bell by HPI. FEATURES: Steel construction INCLUDES: (1) 16 tooth clutch bell REQUIRES: HPI Nitro Star Engine Two 5x10mm bearings, DTXC1535 SPECS: Length: 0.78" (19.90mm) Diameter: 1.1" (28.10mm) JBM 1-11-06 ir/jxs