Check the listing for details. Reedy Sonic 540-M4 or 540-SP5 Brushless Modified & Stock Spec Motors New. Color: Black, Condition: New. Listed at 7.99 USD. Choose from Reedy Sonic 540-M4 or 540-SP5 Brushless Modified & Stock Spec Motors New Internally, the 540-M4 is very similar to that of the 540-M3 that it replaces - it produces the same linear powerband and excellent mid-range feel that have become synonymous with Reedy's modified motors. However, changes can be good when they serve a purpose. In the case of the 540-M4, the inner bearing has been moved so that it is part of the can instead of the sensor assembly, which more precisely aligns the rotor within the magnetic field while reducing noise and vibration. Externally, the motor has been shortened, which results in more centralized weight distribution within the chassis. The reduced length, combined with improvements to the can design, results in a 5-10g reduction in weight. A balanced, high-strength rotor provides powerful fade-free performance. A variety of optional rotors are available to fine-tune for specific applications and tracks. Precision stainless steel ball bearings have been fitted to reliably accommodate high RPM loads. Features: CNC-machined lightweight can Aluminum end cap Lightweight design Low-resistance, silver-plated solder tabs Optimized air cooling Dual precision ball bearings Specifications: Diameter (mm): 35.9 Length (mm): 50.3 Shaft Diameter (mm): 3.15 Weight (g): 160-170 New 540-SP5 Spec Motors:This is the Reedy Sonic 540-SP5 Spec Brushless Motor. Designed to give you legendary Reedy power and performance the SP5 line of brushless motors has been expertly optimized with an innovative unique design.The incredible performance of the SP5 starts with the stator. Designed in-house, the stator's profile is intended to achieve maximum torque and power output without sacrificing RPM. High-quality copper magnet wire, sized to the maximum that the rules allow and wound with care to keep resistance near the legal minimum, is treated with heat transfer epoxy to dissipate heat and reduce internal temperatures resulting in less fade over the course of the race. An oversized collector ring not only dissipates heat, but in conjunction with thick solder tabs, reduces resistance and power loss.A balanced rotor features a high-strength magnet that takes full advantage of dimensional rules to produce fade-free power with maximum effectiveness. The rotor is supported by precision stainless steel ball bearings to accommodate high RPM loads with exceptional efficiency and reliability. Like all Reedy Sonic motors, a high-quality sensor board rounds out the motor's interior.Externally, the SP5 utilizes a lightweight two-piece CNC machined aluminum housing with an aluminum endcap and timing adjustability to accommodate fine-tuning for specific applications. This lightweight package is a welcome way to improve vehicle handling while improving chassis tuning flexibility. Features:CNC-machined housing with optimized air coolingCustom high-power stator designLow-resistance solder tabs and collector ringBalanced rotor with high-strength magnetDual precision ball bearingsAluminum end cap with adjustable timingCompletely rebuildableCompetition provenBuilt to ROAR specificationsSpecifications:Input Voltage: 1-2S LiPoDiameter: 35.9mmLength: 52.5mmShaft Diameter: 3.15mmWeight: 147-151g