You have a 5mm motor shaft and need to drive a 4.76mm (3/16") flexible shaft on a high-torque brush-less motor. Two 40Cr steel CNC flexible shaft couplings are in front of you: one listed at $12.05 and one at $14.82. Both specify the same 42mm length and the same 5mm to 4.76mm fit, so the real decision is whether the higher-priced listing's extra details change your mind.
Quick verdict
Choose the 40Cr Steel CNC Flexible Shaft Coupling when you want the lower listed price and are comfortable with the basic spec set. Choose the 4.76mm Flexible Shaft Coupling 5mm to 4.76mm 3/16" Collet Joint for RC Boat USA when you want a listing that spells out fuel-type compatibility, a silver finish, and a weight estimate, and when the mention of a clamp and motor shaft cutter bar in the package contents sounds useful.
The two options at a glance
| Listing | Listed Price | Value Bar |
|---|---|---|
| 40Cr Steel CNC Flexible Shaft Coupling Fits For 4.76mm (3/16") Flexible Shaft | USD 12.05 | |
| 4.76mm Flexible Shaft Coupling 5mm to 4.76mm 3/16" Collet Joint for RC Boat USA | USD 14.82 |
Both listings describe a 40Cr steel body, CNC-machined construction, 42mm length, and a 5mm to 4.76mm fit for a 4.76mm (3/16") flexible shaft. They also share the same assembly note: the shaft hole uses a negative tolerance that is 0.02mm smaller than the stated diameter, so you may need to heat the part to 200-300°C to get it onto the shaft.
Where each product wins
40Cr Steel CNC Flexible Shaft Coupling Fits For 4.76mm (3/16") Flexible Shaft wins on listed price: USD 12.05 is $2.77 less than the other listing, with the same core material, machining, length, and fit specifications.
4.76mm Flexible Shaft Coupling 5mm to 4.76mm 3/16" Collet Joint for RC Boat USA wins on extra context. The listing calls out compatible fuel types (electric, gasoline, jet fuel/kerosene, nitro & glow fuel), notes a silver color and a 45-55g weight, and describes the package contents as 1 piece of coupling with a clamp and motor shaft cutter bar. If you are building or maintaining an RC boat, that added detail can save you from guessing whether the part matches your setup.
Product notes
40Cr Steel CNC Flexible Shaft Coupling Fits For 4.76mm (3/16") Flexible Shaft
At $12.05, this is the lower-priced way to get a 40Cr steel, CNC-machined coupling for a 4.76mm flexible shaft. The description lists a 42mm length and a 5mm to 4.76mm size, and the package includes one set of flexible shaft coupling. The negative-tolerance shaft hole is worth remembering when installing; the description says the hole is 0.02mm smaller than the marked diameter, so heating the part to 200-300°C may make installation easier. If you are after the essential coupling with the smaller price tag, this one keeps the decision simple. The tradeoff is that this listing gives you the bare-bones spec set; if you value the fuel compatibility and weight details of the more expensive listing, you'll need to spend the extra $2.77.
4.76mm Flexible Shaft Coupling 5mm to 4.76mm 3/16" Collet Joint for RC Boat USA
This $14.82 listing adds a layer of detail for RC boat builders. The same 40Cr steel and CNC machining appear in the specification, along with a silver color, 45-55g weight, and a compatibility list that includes electric, gasoline, jet fuel/kerosene, nitro & glow fuel. The package contents are described as 1 piece of coupling with a clamp and motor shaft cutter bar. Also note the same negative-tolerance installation guidance: the shaft hole is 0.02mm smaller than stated, so heating the coupling to 200-300°C before installation is the recommended approach. You pay $2.77 more than the other listing, but you get a more complete item description. The limitation is the higher listed price at $14.82, $2.77 above the other listing, for the same 40Cr steel construction and length.
Final choice by use case
If you want the lowest listed price and the core specs are all you need, go with the 40Cr Steel CNC Flexible Shaft Coupling at $12.05. If you are working on an RC boat and want a listing that explicitly covers multiple fuel types, gives a weight estimate, and mentions the clamp and motor shaft cutter bar in the package, the 4.76mm Flexible Shaft Coupling 5mm to 4.76mm 3/16" Collet Joint for RC Boat USA at $14.82 is the one to pick. Either way, both are 40Cr steel CNC couplings sized for a 5mm motor shaft to a 4.76mm flexible shaft, and both require the same attention to the negative-tolerance fit during installation.
