Precise Tooth Count: Designed for 17T, optimized for 1/10 RC car performance tuning (acceleration/top speed balance). Model Examples: Fits 5mm shaft motors, compatible with popular RC motors (e.g., 540/550). Design for Traxxas Slash 4X4, Tamiya, ARRMA Granite, HPI Vorza, Kyosho etc. Tight Tolerance: 5mm bore (+0.03mm) with M4 set screws for zero backlash on 5mm motor shafts. Long-Lasting Durability: Black oxide-coated 45# steel resists wear and rust for heavy-duty bashing/racing/crawlers. Ready-to-Use Pack: 3 identical gears per pack for backups or multi-car upgrades. Please make sure your spur gear and pinion gear have the same pitch, or the teeth won't mesh. Compatible Models: For Traxxas: Slash 4X4 (VXL-3S motor), Rustler 4X4, Stampede 4X4 For ARRMA: Granite BLX (BLX 3660 motor), Senton 3S, Big Rock 4X4 For HPI: Vorza Flux, Sprint 2 Flux Motors: for Hobbywing QuicRun 3650, Castle Creations Sidewinder 4, Spektrum Firma 3300KV