This tough steel 17T Mod1 Safe-D Pinion Gear is the perfect part to carry in your RC tool box.Features:Strong and durable steel for long-lasting performance in extreme RC conditions - Precision manufactured wide tooth profile for smooth operation - 'D' shaped hole to match motor shaft profile so drive and brakes are not lost if the set-screw backs out - Suits 5mm motor shaft diameter - Precision manufactured threaded set-screw hole - E-clip supplied for motor shaft pinion retentionIncludes:1 x 17T Mod1 Safe-D Pinion Gear 1 x Set Screw - M4 x 4mm 1 x E-Clip - 3.2mm